Meh, we were great at many things, and horrible at many things. Life is grey, not black and white.
Every nation on the planet has sins. I’m not minimizing America’s; they are grave. But across the world, throughout history every parcel of land was taken, and every nation has at one point exploited it’s people. It’s childish to imagine any nation/culture/people is clean.
Certainly not agreeing with the “back in the good old days” rhetoric. As you point out, “the good old days” weren’t so good if your skin was the wrong color, or had polio, or didn’t want to serve in a war, or many other reasons.