People in South and Central America wouldn't be living the same way as the ancient Mayas, Aztecs, and Incas. Indian civilization saw enormous change over time as well, and no doubt would have continued to do so without European intervention. And I would hesitate to describe South American "democracy," to the extent that it has ever existed, as a Western contribution. It seems to me that the "positives" would depend on who you asked, but I'm not sure that the polities within the Aztec or Inca empires would have viewed Spanish colonialism as an unmixed blessing. In the long term, though, it's hard to argue, unless from an unabashedly Europhilic point of view (like, frankly, that of Niall Ferguson) that native peoples' experiences with Europeans were anything but a net negative.