That is a huge question. And there are many answers. Speaking as an "in law" of a huge Native American family who has lived with and taught Native Americans over the years, I have to say that it depends who you ask or what you're reading.
If you're reading a book written by and for Native Americans, you may find that they feel that the American government had no business trying to "assimilate" Native Americans, who to this day, in some cases, have no interest in being "assimilated," and prefer their own tribal traditions and life ways.
Some other Native Americans might say that the American government had no interest in "assimilating" Native Americans, they just wanted the land they were living on, to help Americans live out the doctrine of "Manifest Destiny."
Others might say that some Americans genuinely hoped that by insisting that Native children be raised in boarding schools away from their tribes, they would learn "American" ways and be able to live in the "white" world more successfully. But research shows that most of those children wound up feeling that they did not belong in either the white or Indian world, once they left school.
Non-Native writers usually agree with one or more of the above as well. But you will have to answer this question using the material you're reading. If it's Bury My Heart at Wounded Knee, how do you feel about what the "Indian agents" and government officials spoke about and dealt with the treaties and reservations they offered the Native Americans? How did Wounded Knee happen, according to the book? I know some descendants of Lakotas who were killed there who are still very angry about that massacre decades later. What does the account in the book make you feel?
There is no way to definitively answer your question as written. You can only read the material you have and decide whether you feel the American government "did the right thing," and whether Native Americans "should" be assimilated or not. To begin, you might ask yourself:
1. What did the American government representatives say Native Americans would gain from being assimilated? What do you feel they would gain?
2. What did Native Americans feel they would lose by being assimilated? What do you feel they would lose?
3. Why did the American government want them to be assimilated? Was it to help the Native Americans or because they wanted their land?
4. How are the government representatives portrayed in the book? Do you think this is an objective portrayal? If not, how and why is that portrayal "slanted" toward a certain point of view?
5. Given what you've read, how do YOU feel the American government should be judged? Did they really care about the Native Americans? What evidence is there that they did or did not?
Bury My Heart at Wounded Knee is a very emotional account of a very controversial time in American history, and we have yet to come to terms with the issues it raises even after all these years. So you can't answer questions of that magnitude all by yourself, once and for all.
But this might help you come up with some ideas worth sharing and debating in class.