I've been reading an interesting book by Charles Mann called "1491". It's presented as an overview of the latest scholarly consensus regarding Native American societies. As you may suspect, much of what you were taught in grade school is wrong. The Americas weren't relatively desolate lands inhabited by few unsophisticated and disconnected peoples. Cities existed as large as London. Technology was different, but advanced in it's own way. Native bows were more accurate than guns, could shoot further, and could penetrate deeper through shields. Suspension bridges existed nowhere else but here. We're still not sure how corn was developed. The population of both North and South America was on the order of tens of millions, approaching 100 million.
Europeans were able to conquer the lands for one simple reason. Disease, which killed tens of millions. Europeans would encounter towns that had been completely wiped out by disease and would conclude that the race was unsophisticated and unintelligent on the basis of the appearance of the few surviving stragglers. It was as if American troops freed Jews in concentration camps, looked at their emaciated bodies, and concluded that as a people they were unintelligent.
A fun brief overview of some of these facts is located at this Cracked.com article. 6 Ridiculous Lies You Believe About the Founding of America.