>> This has a lot to do with why present-day Mexico, Peru, Bolivia, etc. have large indigenous communities relative to Canada and the US: there were higher populations there to begin with.

It's not just large relative to Canada and US, it's absolutely dominant. In Mexico, 88% of population is Native or mixed-Native. Compared to less than 2% in the US. http://en.wikipedia.org/wiki/Indigenous_peoples_of_the_Ameri...