Story Idea: No Lost Civilizations

Reading CNN.com I came across an article about a new ruin found in Peru and how it could unlock clues regarding the Chachapoya people.

It made me think: What if the Spanish came but did not bring disease? Or, what if the natives were immune to disease? What if all of these lost civilizations did not die off but somehow managed to co-exist?

What might the world look like now and what sort of stories would come out of that sort of history?

I can't write it. I don't have the imagination nor the research for that. But it could make a good story.