The usual explanation is that the Europeans lived in much closer proximity with livestock... smallpox probably came from cows, etc.
Also it's generally believed that syphilis didn't exist in the Old World before 1492, so there's at least one disease that probably made the opposite journey.
However, the disease narrative doesn't absolve the Europeans. Nobody forced the European powers to colonize the Americas. If they'd packed up and gone home, even if the Americas had still been decimated by smallpox, they would have bounced back, given the opportunity. Human populations tend to do that.
(The Black Death is sort of an exception, it suppressed European population for a long time, because it kept coming back, killing a bunch of people, and then going away again. But- Europe thrived during that period, the Renaissance was coterminous with very bad bubonic plague outbreaks)
Also it's generally believed that syphilis didn't exist in the Old World before 1492, so there's at least one disease that probably made the opposite journey.
However, the disease narrative doesn't absolve the Europeans. Nobody forced the European powers to colonize the Americas. If they'd packed up and gone home, even if the Americas had still been decimated by smallpox, they would have bounced back, given the opportunity. Human populations tend to do that.
(The Black Death is sort of an exception, it suppressed European population for a long time, because it kept coming back, killing a bunch of people, and then going away again. But- Europe thrived during that period, the Renaissance was coterminous with very bad bubonic plague outbreaks)