Making clear that you feel personally involved when an accusation is made about actions committed not even by your present-day countrymen, but by their ancestors several generations ago. Or in fact, when you get right down to it, the USA wasn't much of a colonizing power - so perhaps not even the ancestors of your own countrymen, but the ancestors of people living in other Western nations.

You're right of course that individuals bear ultimate responsibility for their actions... but if you still consider yourself connected to the ancestors of your countrymen and people even further removed from you, in such a way that you talk about "us" when they are criticized, I'm sure you can see how such thinking leads to people taking "revenge" for events that did not actually directly impact themselves. People's decisions are influenced by what happens around them, and not even only by what happens around them personally in their own time and place, as you are proving yourself.