The Central, South, and North American tribes were not civilized people; they didn’t hold hands, sing kumbaya, and live in peace. The wholesale slaughter of enemies and innocents didn’t just materialize when the Euros showed up. They were brutal over territory and dominance. They fought and warred among themselves and each other long before any modern European set foot on the continent.
As for the land on which Mt. Rushmore sits, READ:
THE FOXHOLE
UNAPOLOGETIC PATRIOT
And forget “Steward of the Environment,” too. Plains tribes would start prairie fires to run entire herds of buffalo off a cliff in order to “harvest” one or two animals, leaving the rest to rot.