>There is an interesting book that explores this question called "Guns, Germs, and Steel: The Fates of Human Societies" by Jared Diamond, although he is concerned more with the success or destruction of early societies. One common theme across the book is availability of resources (including arable land) to the "successful" societies. Another is the ability of large populations to withstand "stress" (war, disease, etc). Obviously there are many other factors, but these two stuck out in my mind, and both contributed greatly to the growth of America.

Interesting. Potentially Canada could have been more successful with a bigger population. We have tons of arable land (for crops like grain) and tons of resources.