We interbred with them. They are not gone, they are assimilated into us. Sure some died, people always die. But their families, culture and genetics are us. We are them.
I once asked a roomful of college students how may of them knew that the Europeans drove the native tribespeople out of Kentucky. The whole class raised their hands. Then I asked them how many of them were part Indian. Almost everyone raised their hands.
We are them.