Modern scholars put pre-Colombian American population somewhere north of 50M people[0]. This number has been hard to measure as most of these people were presumably wiped out by European and African germs well before settlers arrived to most areas and no/few pre Colombian written records exist. Imagine demoralizing and disorienting effect of losing up to 90%[0] of communities population to mysterious disease. I’ve sometimes wondered if the lack of this wonder weapon is reason behind why Vikings and others that reached American continent before Columbus did, never established permanent lasting and expanding colonies.

Imagine if it would have worked the other way around - indigenous Americans carrying a germ that would have traveled back to a Europe making great plague look like a child’s play.

[0] https://en.m.wikipedia.org/wiki/Population_history_of_indige...