One of these days I want to do that project I've been noodling around for decades that's just "all the parts of Hetalia's concept and fanfic scene I find compelling without any of the real world stuff that makes it fraught and potentially really icky."
Secondary world dieselpunk fantasy with people who are the personifications of... lands? Countries? Kindreds, tongues, peoples? Nations? States? Which is it? Does it matter which it is?
If you are one of these nations, you are immortal as long as whatever-it-is-you-are endures. You cannot die in a way that matters. You can be blown to bits, and you will wake up in a crater a week later. You can- and want to- fight alongside your humans, if there is a war, and work alongside them if there is a peace. You want to keep them safe.
You are also fully expendable. As you can't really die, you're frequently assigned to suicide missions. (If you're not assigning yourself to them in the heat of battle.) You've been through more trauma and pain than you care to remember. If you're an older nation, you've probably got several hundred years of PTSD that you've never worked through, and are reacting to things accordingly.
You're the personification of your people. That means you have to reflect them. Your opinions, your ethics, your most intimate personal relationships- even your tastes in music or aesthetics- are expected to change at the drop of a hat. (Do they actually change with your people's opinions? Or are you just a very good actor?)
You likely (especially if this is WWII-era dieselpunk) have a terrible, unreasonable boss. They might see you as a pet, a toy, a surrogate child, a living weapon, or a testament to the success of their horrid personal philosophy. You spend way, way, way more time with your boss than any normal human would, and spend most of your energy trying to curb their worst impulses.
In wartime, you're an unspecified petty officer- not high enough in the ranks to attract anyone's attention, but high enough to do some good. In peacetime, you're a mid-ranking civil servant with a position that would normally be given to someone's useless nephew. You do a lot of Unspecified Paperwork.
You're part of the worst club in the world. Nations know nations, whether from proximity or a sixth sense, and you've spent a lot of time talking to each other at diplomatic events, casually or otherwise. You're friends, in a way. You could stab each other in the back at any moment, based on what your shitty fucking bosses want you to do. Most of the older nations treat that as an occupational hazard; the younger ones (especially the more idealistic ones) still get their feelings hurt over it. Some of your bosses - the old-fashioned sort, Kings and Queens- think that an alliance between nations is tantamount to a marriage. (Is that how you feel?)
This is all incredibly compelling stuff and would be way more fun to play with in a secondary-world setting where any Unfortunate Implications are A) there on purpose, B) thematically relevant, C) not treating real world atrocities as angst fuel for fic.