One question I've had about domesticable animals that I've never seen addressed - likely because, to be fair, it's unfalsifiable - is How many of the North American large animal species wiped out in the first waves of human settlement would eventually have been domesticable? If the answer is "some, probably" (which doesn't seem unreasonable), then continuous human habitation is a relevant (continental) factor for cultural advancement.

There were horses, at least, not tremendously different morphologically from Asian species, but which (most likely) had not inherited an instinctual fear of humans.