It is absolutely correct to say that the United States and individual states committed genocide(s) against Native American populations. For more, see this:

https://www.reddit.com/r/AskHistorians/comments/6kywre/monday_methods_american_indian_genocide_denial/

and

https://www.reddit.com/r/AskHistorians/comments/6mg3j3/monday_methods_american_indian_genocide_denial/