In fact, not all native americans opposed the conquest of America. Some of them allied with the europeans, because they had wars with other native americans or because they considered them divine when they saw them mounted on horses and carrying fire weapons. 80 000 - 200 000 native americans supported Spain in the conquest of the Aztec Empire (source: wikipedia)

Although europeans did not treated native americans well at all, there was not extermination. Most deaths were caused by unintended transmission of illness.

By the way, did you know that the Norse discovered America centuries before than Columbus? (source: wikipedia again )