I don't think it's genocide, honestly, because the US did the same to anyone on what we now know as the US. It doesn't matter if there was one race or thousands, the US would have still done the exact same.
Maybe genocide in it's rawest form, that the US did it to that one culture as much as they did. But certainly not as used in "The US was a genocidal maniac" type sense.
Course we also did the same to the poor and downtrodden, the irish, the blacks, the Spaniards, the Mexicans, the "South", and on a non governmental role, homesteaders, cattle drivers, gold miners, religious cults, etc.