I was wondering how Diamond's theory worked on North America. If there were tons of healthy people with cultivated land and buffalo to eat, why were they so far behind the Europeans?
Why not? In a world of isolated populations there are bound to be different levels of development.
In earlier years the Chinese were centuries advanced over Europeans.
Even as Cortez arrived in Teotehuacan, the city out-shone any city in Europe, in size, public utilties, wealth, cleanliness, and beauty.
Too bad that they were not genetically diverse enough to be able to deal with the diseases that came with the Europeans, or that they had not developed sea-faring first. History is full of accident.
One has to accept that contact between the new and old world would have taken place at some point between 1492 and, say 1850. It matters not when it happened; what is important to realize is that whenever it happened the result was preordained. Disease would wipe out the Indian populations with no intent to do so by the Europeans. This would have happened even if the Americans had first gone to Europe, as they would have taken the diseases back with them.
That's how the diseases were spread through out the Americas in the years after first contact, to populations that had no idea of the existence of Europe, 'white" men, or ships.
One might profitably aske the same question about the Africans. There were a lot of them, and they were very far behind the Europeans, too. There doesn't seem to be any reason to assume that technological progress has to go hand in hand with health and cultivation.
One theory I've read is that, for whatever reason, metals in the Americas are more difficult to mine, whether due to geology or geography or whatever. So, the native populations were unable to make the step from stone tools to metal tools.
I don't know how accurate that is, to tell you the truth.