In response to several of the posts made. I believe the estimate made by Diamond for the population of the Americans at the time of Columbus was roughly 100 million people. In this theater one cannot downplay the sheer destruction caused by new diseases introduced to Native Americans. Many powerful tribes(including the Mississippians) were wiped out by disease before Europeans even explored the area. Another estimate used in Guns, Germs and Steel was that disease killed roughly 80-90% of the Native Americans after Columbus. If these figures are even remotely accurate how can a person try to compare European colonization with disease as opposed to without it?

Had disease been a non-factor I feel the Americas by and large would not have been colonized until the 19th Century, therefore comparable to the history of India. Remember the Europeans at the Jamestown colony failed at survival for nearly 25 years(including Roanoke). Without a constant supply of food from Europe any army would have simply starved to death if they were not able to raid supplies from the natives. Considering how much trouble the Europeans had dealing with the depopulated Native Americans, how would they have done against more numerous and cohesive foes?