[petesergeant]

I'd be interested in an alternative world history where the first humans into North America had domesticated and saved the local horses that were kicking around, or the Vikings had left a bunch on their earlier expeditions. Alternatively where the Vikings had managed to give the locals small pox and other European diseases en-masse before leaving.

[mmustapic]

Not exactly your scenario, but The Years of Rice and Salt, by Kim Stanley Robinson, has Europe almost wiped out by the Black Death.

https://www.goodreads.com/book/show/2723.The_Years_of_Rice_a...