I conclude from what you write, you have native american heritage. And really, it is a shame that these cultures were destroyed. It says all, that today "native americans" are grouped together, as if it was one culture, while in reality it was many different. The same is true for africa, we often group that together, but before europeans destroyed the native cultures there existed a lot of different kingdoms.
And this all is a loss for all of humanity in reality. A diverse and rich cultural heritage is a big boon. Modern cultural products can rely on that. Movies, music, books and even games. Look alone how God of War forms a cultural heritage that wasn't destroyed into a great game. There are cultures that are not existing anymore, but their heritage is in parts intact. Take Babylon, Sumer, Ur. The Gilgamesh-myth is still known today. How many myths like that are now lost forever, because american and african cultures were destroyed?
And it should be more in our minds how badly american and african people were treated. We have in germany a culture of remembering what we did to jews, roma, gay people and communists. School classes have days they travel to the former KZs and learn what happened there. Do similar things happen for native americans and africans? I think we should all be aware of the crimes our ancestors commited. Not to feel guilty (I was and I am no Nazi), but to learn from it and learn to avoid similar things happen in the future.
I do, can still see it in my father and me as have naturally darker skin and hair. Sadly, when my great grandmother was adopted she was taught to give up her culture as it was thought it was best to modernize and make them more European.
I would caution saying they were destroyed. This creates the idea that the tribes are a relic of the past no longer present. They are still around, and still struggling. There was a big issue last year in the Dakotas when a pipeline was redirected away from the city and went across native land. The local tribes protested fearing the damage it would do to places they feel are sacred. They failed, the pipeline was built, and it had a leak causing environmental damage. Sadly this doesn't get much attention in the national media because those on the periphery become invisible.
I think people associate guilt and blame when they shouldn't. Americans have an intense desire to be "good guys" that we struggle coming to terms when we fail to live up to our lofty ideals. We don't talk about even recent history of interfering in elections or supporting tyrants. We get very uncomfortable, so we prefer ignorance. This is what leads to many mindsets about how "We're Number One!". It isn't to condemn us, I love my country and love living here, but I think we can confront our faults and strive to be better, otherwise we have no context for our society or the world.
Yes, you're right, many tribes still exist and struggle to keep the culture. Still, some tribes are actually extinct and even for the still existing tribes, a lot of the cultural heritage is lost. Which is a shame.
Anyway, I hope the US finds it way to accept the culture of the native americans into their general culture. This could help to define a very own american national identity. So far the US seems to be mostly a european culture. I bet in school you all learn Shakespeare and ancient greek history. If you would also learn american history before 1500 and native art, it probably would already change the understanding of your own nation. Do you have classes at school/college to learn native american languages? I guess there are classes for spanish, french or italian.
I agree with you on the guilt and shame thing. The problem herein probably is the the black-and-white thinking. Nobody is singularly "good" or "bad". Another thing is, that I get the feeling, that citizens of the US often very strongly identify with their nation. That's a thing that can change. We in germany often criticize our government or our foreign policy, if we don't agree. That doesn't mean we don't feel as germans or want to live elsewhere. It is hard enough to take responsibility for my own actions, it is often not easy to see my own faults and admit them. Doing the same for my country is impossible. I see myself as an own person in the country, the course of the whole is defined by 80 million people and I can clearly say I don't stand behind EVERYTHING my country does. So a 'my country is #1' mindset looks for me very much like something to avoid pondering consequences or ethical implications. I might be wrong, but it seems for me that way.