Even if America does things I don't agree with, or previous generations did things in my name ("For our children, and future generations!") as a reasonable, responsible American, I acknowledge that my parent's generation may have done some ****, in my alleged name, that I don't agree with. Without accepting personal guilt (as i never shot a Vietnamese, nor killed an American Indian nor ever owned another human soul in servitude), I can at least acknowledge what my forebears did, "allegedly" in my name ("For future generations"), right or wrong.
I love my country. But I hate the politicians. And I am surely not taking the rap for their crimes or participating in putting the rap on the other little guys.
Did Calley go berserk? Yes. But who put him there on a lie for the express purpose of killing? LBJ. Ho Chi Minh did not invade the US. This was no just war of self defense. The war itself was a crime. And if you want to accept a share of national guilt for that, it is your right, but I don't recommend it. I do recommend trying not to repeat mistakes.
And I am sure you notice, no one addresses the question of why dropping bombs and wiping out villages is not a war crime, only when it's done in person is it horror.