The American government, and governments before it, did commit genocide, most particularly against Native Americans -- you may be interested in these older threads from u/snapshot52 on the American Indian genocides:

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/