The vast majority of people on this planet are descendants of cultures that, at some point, were dominant in their area by conquering their neighbors. Vikings, Romans, Persians, Chinese, Russians, Inca, Aztecs, Spanish, French... I'm sure others can give more examples. Given human history, I'm pretty sure that those who did not (or have not) done so failed due to a lack of _means_, rather than will.
Yes, I'm sorry that the founders of this country completely screwed the natives. That was a terrible thing to do. (My ancestors didn't come here until a century later.) What would you have us do? How can one meaningfully repair those wrongs? We've seen in Israel the extreme difficulty of resolving the "I was here first" group's claims with "But my family has lived here for hundreds of years" group. It's like someone coming to take your house because you bought it from someone whose great-grandfather stole it from his great-grandfather.
It saddens me that we, as humans, seem to be unable to agree on a way to live together harmoniously. I'm sure that advocating forgiveness for past wrongs is a position that I only take because I am not from the group that was wronged, but ... where does one go?
A very large number of Americans are descendants of Native Americans, or blacks. Possibly also 'whites' at the same time (though many of those 'whites' were later non-Anglo arrivals).
So you are in the odd position of justifying anger by (say) Dutch people against Americans who are related to them, or to Italians who arrived in 1920, or hispanics or blacks or Native Americans.
Because, don't you know, non-Americans have every reason to be displeased with modern Americans on account of things some Americans did a long time ago. But the Dutch (as one example among many), of course nobody of that nationality did anything back then.
When people talk about privilege (though often in a gender context), this is exactly what they are talking about. Or th joke about George Bush being born on third base, thinking he hit a triple.
Those past actions by other people put you in a position of wealth and power >90% of the world's people, and you didn't do any of it, you just received the benefits, and (probably, I don't know you personally), haven't returned ill-gotten gains that came to you. As such, non-Americans have every reason to be displeased with modern Americans.