Anthropology

what made Neanderthals go extinct.

The comparison to Europeans arriving in the Americas doesn't mention a few things that I think are worth considering.

European weapons were more technologically powerful than the weapons of the Native populations of the Americas. Was that true of early Homo Sapiens who encountered Neanderthals? If not, then something besides warfare would account for Neanderthal extinction.

Huge numbers of Europeans flooded into the Americas, with conquest and control of natural resources as intentional goals. Was that true of early Sapiens when they entered Neanderthal territory?

After the encounters of Sapiens and Neanderthals, only people with a mix of the two human species left descendants into the future. "Pure" Neanderthals did not continue to exist. Also, "pure" Sapiens no longer existed, except in sub-Saharan Africa where Sapiens did not encounter Neanderthals.

The same is not true of Native Americans and non Native people (Europeans, Asians, Africans) in the Americas today. So it looks like there was more interbreeding between Sapiens and Neanderthals than between Native Americans and non Native people.

There was probably some fighting between Sapiens and Neanderthals over territory and resources. Even chimp troops fight other chimp troops for territory. But, despite the fighting, there must have been a lot of interbreeding to produce only mixed descendants. Did Sapiens men kill off Neanderthal men and take Neanderthal women as captives? Maybe, IF they had weapons and war strategies that were superior to the ones that Neanderthal had.

Or maybe the interbreeding produced a stronger genetic mix to survive environmental changes in climate and habitat.

Maybe the number of Sapiens entering Neanderthal territories was just larger than the Neanderthal population so that interbreeding caused "pure" Neanderthals to go extinct as as a separate species.