US government displaced and murdered native Americans for a long stretch of history. For multiple tribes this included extermination based on ethnic group. US soldiers acting in official capacity killed defenseless Native American civilians including young children based on their ethnicity. The genocide of Native Americans is well documented.
"Genocide: The systematic and widespread extermination or attempted extermination of a national, racial, religious, or ethnic group."
But I don't think that the giving of land (no matter how terrible the land is) for a group to live on truly counts as "attempted extermination".