Practically every US citizen who is 3rd or 4th+ generation American can point to ancestors who were screwed over or cheated out of their land or possessions or even their lives in one way or another. Practically everyone on earth can look back and point to misery inflicted on their ancestors. One of the great beauties of America is that every generation has a better chance to overcome the misery inflicted than the previous generation.
Humankind is an evolving species, and I can't think of a place on earth that has evolved better than the good old USA.