The Native American civilizations never had a Neolithic Revolution, and never domesticated any animals except the dog, which Europeans also had, if you will recall.
And, at any rate, are you forgetting syphilis, which came from the New World.
At a minimum we should have installed bubbles over every American Indian community to protect them from our horrible diseases because they were all healthy and carbon conscious and just how we should live today.
I'm not sure how the weak and frail fit into the survival of the species under that scenario, but I have a hunch.