Indians were nomadic tribes. Europeans were settlers, not illegal aliens.
I’m aware of all that (although, not all tribes were actually nomadic). I was essentially paraphrasing an old joke — the punch line being: “bad immigration policy”. The fact that the aboriginals were incapable of preventing the in-migration is irrelevant. The point was — whether you call them “settlers”, or “illegal aliens”, or “refugees”, or even “legal immigrants” — when a critical mass of them arrive on your shores and make no effort to assimilate, you can kiss your culture and sovereignty good-bye.
(Just to be clear: immigration can be very beneficial — up to the point, where it becomes indistinguishable from an invasion.)