According to Guns, Germs, and Steel, why were Europeans able to conquer many of the groups in the Americas?

Diamond
argues that Europeans were able to conquer the natives of the Americas because of geographical
luck.  The Europeans had had better geographical luck and, therefore, they had the guns,
germs, and steel that allowed them to conquer.

The Europeans had been born in
a continent that had had agriculture for much longer than the Americas had.  Their agriculture
had been more effective as well.  This is partly because there had been more species of large,
domesticable animals in Europe than in the Americas.  It is also because the types of grain
available in Europe were more nutritious than those in the Americas. 

What
this meant is that Europe was able to have larger, denser populations from much earlier than was
the case in the Americas.  This gave them the ability to create more kinds of technology.  It
also gave them the massive populations and the proximity to animals that led to the existence of
epidemic diseases.  It was the technology and the diseases that were mainly responsible for the
conquest.

Thus, the Europeans had technological advantages and the advantages
conferred by their diseases.  These factors, which were caused by geographic luck, allowed them
to conquer the Americas.