While South America only has four canon Legacies recorded, the Tlacique from Mesoamerica are described as having had a presence amongst the Incans and the Cipactli were found in northern South America. There are likely other Drowned Legacies in South America that have not disclosed their existence to wider Kindred society or are erroneously considered Caitiffs (Clan-less). I have also included two Legacies from Brasil in the Darkness and one personal homebrewed Legacy.
While the out-of-game reality is that likely the World of Darkness authors had little interest in or knowledge of pre-Columbian South America, we can make some in-game assumptions based off what is written. The Drowned here were less organized pre-colonization than their Central American cousins and likely were heavily suppressed by the powerful Bastest werecats of the continent, the Balam werejaguars and Pumonca werecougars. This meant that they were less able to openly rule or present themselves, but would've still had strongholds similar to European Kindred in areas with heavy Garou activity.
("Art by: Luis Eduardo", A mensagem Final da Mãe)
In modern nights the Sabbat and the Camarilla battle for control of many South American cities, with the Sabbat historically being the more dominant force. As the Sabbat have taken a hit in recent years between the Beckoning (which the Drowned do not experience) and the betrayal of many Lasombra elders, a power vacuum has opened up that many, including many Drowned, are looking to exploit. Indigenous Drowned, as you'd expect, are generally not very happy with the colonizing Kindred. Many of these Cainites are called pishtaco by the Drowned, inhuman monsters benefiting from the displacement of their native cousins and preying on the colonized. While the Drowned are far from heroes, being predators in their own right, their elders have witnessed all the atrocities of colonization first hand and their neonates come from a world still under attack from land developers, foreign-backed coups, and exploitation.
Cupendiepe
("Art by Luis Eduardo, original for Brazil in the Darkness." Cupendiepe, Mensageiros da Noite.)
The Cupendiepes are a bat-like legacy hailing from Brazil. They see themselves as kin to the vampire bats of the region, often sharing caves with the creatures. Historically the Cupendiepes have remained isolated from the rest of Drowned society, preferring their jungle cavern homes where they collect with others of their Legacy. When interacting with outsiders they tend to be hired for specific tasks like spying or transporting long range messages that can't be sent traditionally, but they prefer to avoid direct confrontation whenever possible. Cupendiepes are reputed as a mercenary Clan with no true loyalty outside of their fellow Legacy members. They have a strong Legacy culture, and are very social and loyal to one another. Sharing resources and information is expected between Cupendiepes, and betraying your Legacy is usually met with death. Their Clan Disciplines are Auspex, Obfuscation, and Journey, a custom Discipline outlined in Brazil in the Darkness that allows them to take on the traits of bats: communicating silently, turning into a bat, controlling bats. Their Bane is Chiropteran, giving them a bat-like traits that are obviously Masquerade breaking. Their Compulsion is Cowardice, causing them to be compelled to flee from conflict or danger when triggering a Compulsion. This Legacy is homebewed by Brazil in the Darkness and is based on the folklore of the Apinayé people of Brazil.
Kaledjaa
("Art by Luis Eduardo, original for Brazil in the Darkness." Kaledjaa, Setas de Ceiuci.)
The Kaledjaa were traditionally an order of warrior women who see themselves as tasked by Ceiuci herself, legendary mother of the Drowned Legacies, to maintain spiritual order and Cosmic Balance. In modern nights some rare men have joined their ranks, but their goal remains steadfast. The Kaledjaa are fighters above all else, training relentlessly from the moment of their Embrace in secretive lairs throughout South America. They seek out Kindred and other supernatural creatures that they feel threaten the balance, which these nights are plentiful - more than the Kaledjaa could ever hope to remove. But that does not stop them from trying relentlessly. Their Bane is a curious one - the Mouth of Ceiuci, where extra toothy mouths will form (one per Bane Severity) somewhere on the Kaledjaa's body. These mouths are functional, capable of biting and occasionally will speak separately of their host. The Kaledjaa believe this voice is that of Ceiuci and are taught to heed their orders. The mouths are often able to be hidden, so long as they stay quiet. Additionally, the mouths are gluttonous - the Drowned must make an extra Rouse Check every morning to see if they gain Hunger, equal to half of their Bane Severity, rounded up. The Compulsion of the Kaledjaa is Obedience - when triggering a Compulsion one or more of the Mouths of Ceiuci speak an order. The Drowned must follow the order or face a -2 penalty on all rolls not related to carrying out the task until the task is complete or impossible to complete. Their Disciplines are Fortitude, Celerity, and Scourge, a custom Discipline that gives them abilities related to punishing problem-makers. This Legacy is homebewed by Brazil in the Darkness and is based on the folklore of the Macurapes people of Brazil.
Kalku
("Art by Luis Eduardo, original for Brazil in the Darkness.", Kalku, Pastores do Rebanho.)
The Kalku of Patagonia are notorious for their ability to physically puppet victims using some sort of Blood Sorcery. They fear reprisal from humans more than other Drowned because they are as vulnerable to manmade weapons as any human would be, resulting in them focusing greatly on maintaining power over Kine as much as possible. Kalku want to be fully in control of the situation, as they suffer from extreme paranoia. Their Clan Disciplines could be Blood Sorcery, with a homebrewed power or two to bloodbend people, Presence, and Dominate. Their Bane is Mortality: they take aggravated damage from kine weapons that would normally be superficial, with the aggravated damage portion being no greater than their Bane Severity. Their compulsion is Paranoia, thinking someone in their vicinity is out to get them, compelling them to take defensive action immediately. Brazil in the Darkness' custom Discipline for the Kalku is called Pantomime, which allows them to directly control Vitae, giving them their signature Puppeteering. This would replace Blood Sorcery, of course.
Karai Pyhare
("Art by Luis Eduardo, original for Brazil in the Darkness.", Karai Pyhare, Senhores da Noite.)
The Karai Pyhare are native to Paraguay and the surrounding regions. Little is written about them, save a prophecy of a powerful Drowned that will reclaim power and that they have a severe agoraphobia. They are based on the folkloric creature of the same name from Paraguay who seems to be a trickster. Pulling from this lore, I would give them the Clan Disciplines of Animalism, Obfuscation, and Celerity. Karai Pyhare are natural masters of espionage and secret keeping, previously using their abilities to take on the role of kingmakers and spymasters in Drowned society. These nights they do much the same, utilizing their affinity for stealth and confined spaces to act as assassins, thieves, and spies. Their Agoraphobia could be their Bane, suffering penalties to rolls when exposed equal to their Bane Severity, and their Compulsion could further play off this, causing them to find whatever environment they're in unsafe, compelling them to hide. Brasil in the Darkness gives the Karai Pyhare a custom Discipline called Ardiz, which allows them to contort their body and change their voice. If taking this, consider replacing Animalism.
Lostundo
("Art by Luis Eduardo, original for Brazil in the Darkness." Lostundo, Imitadores Sedentos.)
The Lostundo are native to the northern regions of the continent. They have the ability to take on the appearance of victims they feed upon, but have difficulty using their Disciplines in homes or havens unless they have consumed the homeowner's blood. In modern nights Lostundo have a reputation for working with or directly controlling drug and trafficking cartels, using their position for feeding and power. Their ability to transform their appearance is a bit hard to nail down, it could be an Obfuscate power locked behind the Lostundo Legacy or a Loresheet, it could be a Blood Sorcery Ritual that requires the blood of the victim as an ingredient, or it could be part of a custom Discipline. Their Clan Disciplines could be Obfuscate, Potence, and Dominate, while their Bane is Guest's Etiquette: the Lostundo takes a penalty equal to their Bane Severity whenever they use a Discipline in someone else's home or haven, unless they have drank at least one Hunger's worth of blood from an owner of it. Their Compulsion, Kine Diablerie, results in them mixing up the memories and traits of recent victims with those of their own when they trigger a Compulsion. Brazil in the Darkness gives them the custom Discipline Expolio, which allows them to impersonate and steal the identities of those the Lostundo has fed on. This would replace Obfuscate.
Unhudo
(Corpo-Seco by Mari Morgan)
The Amazonian Unhudo, also known as the Corpo-seco, are spider-like in their hunting, able to climb extremely well and acting as ambush predators. In days past they would hide in trees, attacking passerbys, and while some still do most have adapted to climbing the walls of buildings in cities instead. This has allowed them to adapt to urban life well, lurking in alleys, under bridges, and in other hidden locations. This secrecy is necessary because their Bane is their corpse-like appearance, which has caused some to speculate that they are related to the Cappadocian Clan, now Hecata, but they don't display any talent at Necromancy so they do not associate with Hecata. The ability to climb walls in V5 is a Blood Sorcery Ritual, but perhaps this could be replicated by a Level 2 ability in Celerity, maybe Amalgam with Animalism for the spider connection. Their Clan Disciplines could be Celerity, Animalism, and Obfuscation, making them fast and stealthy ambush predators. Brazil in the Darkness' Discipline for the Unhudo is Reflux, combining the ability to climb with a connection the Underworld and the ability to sleep within trees. This could replace Animalism or Celerity.
Supay
(Supay by JavSama on DeviantArt)
The Supay hail from the Andes, tracing their lineage back through various Andean civilizations. Mystics gifted with the power to see the future and control the very shadows, they often acted as advisors both to powerful kine and to other vampires. They were traditionally accompanied by a black dog familiar, representing the souls of the dead, which played into their role as a spiritual being. In modern nights Supay often act as cult leaders, taking advantage of the disenfranchised to obtain a steady supply of blood. When shirking this role, they may completely reject society, using their shapeshifting and superior senses to live on the fringes. Their Clan Disciplines are Oblivion, Animalism, and Auspex, with their Oblivion usage favoring shadow control / Obtenebration abilities rather than necromancy. Their Bane is Shadow Made Flesh: when the Supay uses a Discipline their flesh becomes lightly incorporeal, temporarily giving them a penalty to interacting with items, people, or other physical things equal to their Bane Severity. Their Compulsion requires them to bring balance to something around them immediately. This Legacy is homebrewed by me, I felt it weird that there wasn't a Legacy associated with the Andean highlands so I wanted to make one. I first considered making one based on the pishtaco, but decided that it was far too tied to colonialism to be written as a pre-colonial vampiric bloodline. A wealthy white Ventrue pishtaco with the Organovore flaw, literally consuming impoverished Indigenous people, would make a good villain for a Drowned Chronicle. Instead, the Supay are inspired by the God / underworld spirits of the same name in Andean mythology.