And I think it should be mentioned that Guns, Germs and Steel is rather extreme in suggesting an 'geological determinism.'  While his arguments are generally quite good, there is simply quite a bit more happening. A nice book to balance this is Ian Morris, Why the West Rules--For Now.
 Jarred Diamond actually warns of this determinism fallacy, but the book certainly left me with the impression that such a determinism exists.
 http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4959.2008.... (paywall)
One way to phrase the distinction is that no one really expects huge empires in Antarctica, so everyone admits there's some role to the environment. GGS talks about more complicated effects that the environment has, without saying anything about the outcome being deterministic. It argues that the odds were somewhat higher of Europe invading North America than vice-versa, and doesn't even try to quantify by how much.
According to the book, the reason China has a large stable empire was because of China's geography, which was mostly flat and well-connected by the Yangtze and the Yellow river. With few geographical segments, this led to the people being less likely to form 'tribes' and more likely to be united culturally.
This is in contrast to Europe, which has a large impassible mountain range in the middle, and lots of peninsulas and small rivers, forming natural boundaries. This led to Europe being more diverse culturally.