Personal notes from Inagaki's mid-final cour Q&A, focusing on the Americans:
Stanley's an amazing marksman, so he'd be able to snipe a small target like the revival fluid. If the bottle explodes, the revival fluid could fall on someone else below like Maya. The probability is low, but it's not impossible. Stanley's not divine. But if he shoots, the Xeno 100% wouldn't be able to continue science. The host adds that more than the operation, Stanley acted for Xeno's sake. Inagaki noted that there's no traditional command structure remaining, so it's all up to Stanley's own judgement. From a military perspective, Stanley can do whatever he wants.
Stanley was left petrified because despite Xeno becoming friendly with Senku and co., Stanley's dangerous. He's too strong of a wild card. He's too powerful. As a hostage, he's the no. 1 way to keep Xeno in line. Xeno has no idea where his statue is being kept. If Stanley's statue gets stolen, it's all over.
Stanley got into guns because he's American, and had easy access to guns. Inagaki jokes that Americans like guns for no real reason, sort of like how Japanese people like katanas for no real reason.
Inagaki is not a legal expert and gives that disclaimer himself. Regarding Stanley standing trial, he posits that in a prototype nation, a person carrying out an act of war in defense of their own country is likely not a crime. If that was the case, then both sides would be guilty. He wonders if a trial is even possible in the first place, because the KoS isn't from America and at that time, Xeno was unquestionably the nation's leader. Thinking that way, Stanley wouldn't be charged with a crime. But depending on the witness testimony, there could be ambiguity. (1)
The Americans didn't have a pro cook revive on their side. As soldiers, they're very efficient. Their food is something like Calorie Mate. The no. 1 feeling would be that something balanced is best. So they were very happy to be able to taste Francois' cooking. (2)
Stanley and Xeno likely didn't imagine them moving around that much. It's highly likely they've always been in that area (Boston) Inagaki does not confirm that Xeno went to MIT. (3)
More confirmation that Xeno was arrested following the football incident, but was still hired by NASA afterward. (4) Stanley doesn't seem like the type to get caught and vanished from the scene like Golgo 13. On the other hand, Xeno was very dignified. He'd say something like "That was truly an elegant shot."
Xeno started styling his hair into a pompadour because his hair kept getting in his face and it was hard to concentrate on work.
Senku and Xeno admire each other's talents as fellow scientists on equal footing.
Xeno designed the clothes in the American settlement, but someone else was in charge of creating them. There was likely an unnamed person with a talent for sewing and clothing construction in the group.
If Xeno had to survive on his own the way Senku did (without Stanley or platinum), he would have been able to. He doesn't lack in stamina, he's not particularly skinny. But once Stanley revives, his physical strength is very valuable.
Senku, Xeno, Chelsea, and Sai, who is the best teacher among them? Senku is very talented at teaching, but the one with the most skill is Sai. Sai was a teacher prior to the petrification, teaching math. Xeno is the type to naturally explain things, but if he feels that the person he's trying to teach is being uncooperative, he will drop them. Chelsea speaks in Chelsea language. It's hard to understand her.
Stanley isn't very good at looking after people, but he is very capable. Inagaki thinks the uniforms everyone was wearing at DARPA were extremely cool (he says this multiple times).
Xeno deeply concentrates on his work, his eyes go wild. But he's the type that, for example, from 11PM-midnight, abruptly halts, stops everything, and falls asleep. When the time comes, he falls deeply asleep. He thinks it's pointless to pull all-nighters.
Byakuya didn't know Senku was emailing Xeno (Inagaki emphasizes this three times). If he knew he'd say "Amazing!" He'd be excited for his son. But he definitely didn't know.
Stanley left Luna behind after sniping Senku because it's not his job. "This is not my job" (Inagaki says this in english). If he were to take on extra work, that could be detrimental. He didn't know that Luna wasn't in any danger and that none of the other members of the KoS would try to kill her. But he's not taking any unnecessary risks the way Carlos and Max would.
Questions he does not answer:
If the petrification didn't happen, and Senku reunited with Xeno, would they have still clashed? (He does confirm that Senku would likely go to NASA because of NASA's massive budget)
What Stanley was like in the Marines? What was he like (at his rank, implied) so young? Was he strict like a drill sergeant?
The entire postcanon legal system is a mess. There's never any point where they make clear if present-day international law exists in the stone world. As of the story's text, laws don't really exist. If international law does exist, then Stanley did commit real war crimes and that's not the same as what the KoS did. Inagaki's kind of equating engagement in hostilities to war crimes, and that's not the same magnitude. And if international law exists in postcanon, does that apply retroactively to a time when laws were not clear.
Sacramento and the California Central Valley is one of the most abundant places in the nation. Stanley and the rest of his military squad would know how to forage and eat bare bones just to survive, but they wouldn't have to. There's so much around them that they don't need to resort to bland cooking. They may not have anyone with Francois' talent, but they have enough options that they can still make edible food. The Sacramento River is right there. Also Xeno would not be tolerating eating gelatin and protein bars forever.
Boston may be canon but it's dumb as hell. Inagaki googled 'MIT location' and called it a day.
Japanese gun law is significantly stricter than American gun law, so Inagaki is making assumptions. Re: the railgun, Xeno never broke any laws. He would not be charged with a crime, he would not have to see a judge, he would not have anything on his permanent record. He would have been arrested by the police and held for probably a few days though. (According to the fanbook, Xeno was arrested a few months after the football incident, not directly afterward. Incident happened in February, Xeno was arrested in August)