What kind of man was Steve Rogers, to fight for America with his background?
In the original comics, he was Irish from the Lower East Side. This means he was probably Irish Catholic from the tenements, which meant he was considered by most Americans with power (maybe) one step above dirt.
On the other hand, he was a tall, blond, blue-eyed man, the Nazi ideal. The Catholic church coexisted with the Nazis without severe discrimination. Many Irish were allied with the Nazis.
He grew up in a multicultural multiracial neighborhood and would have known many people that the Nazis considered less, but he would not have been one of the people they considered less due to their genetics.
So what kind of man could look out, see the horrors that are being done to other people, and choose to ally with the people who treated him and many others like dirt instead of the ones who would treat him extremely well but commit atrocities against others, and continue to do so over the course of an entire war?
And for a laundry list of references related to this...
https://markhumphrys.com/sfira.nazis.html -- Neemers
[AN: Owing to my dreams of actually putting a price tag on my anthology, I can't actually write about Captain America. So let's make up a strikingly similar hero]
A hero fights, not because they like fighting, but because some evil must be stopped with brute force. Two factions are at war, and in some ways they are alike in villainy. However, there is a key difference. On one side, the downtrodden are still permitted to have a voice. People have the freedom to speak. The freedom, also, to choose who they listen to. The freedom to act upon their convictions or to choose to remain complicit in tyranny.
Interestingly, the nation with those freedoms had the other crib notes from it and turn the philosophies just three degrees more evil. But that's not why we are here.
Picture a hero. Good. Now picture almost the exact opposite of that. Scrawny, weak, always sick. Culturally, they are the lowest of the low. The most reviled. The hated. However, this hero is lucky enough to exist in the nation that allows such people to live their own lives. This hero can speak. This hero can listen. This hero lives in a cluster of other such reviled and hated folks, but they do not hate. These rejected persons are their neighbours. Friends, allies, connections to acquire what is needed. A network who shares what little they have, for the betterment of all.