>I heard someone in the media say "The 20th Century was the American Century". I think this is true. But how did it happen?
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>The US was late to the Industrial Revolution because of its civil war. In addition, the US was quite isolationist. In the late 1800's and early 1900's Americans started to innovate and where at the leading edge of electricity, radio and flight. The two world wars gave the US economy a good kick in the pants.
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>Why didn't Mexico or Canada beat the US in growth? The European countries were for the most part flattened by World War II and in economic disarray.

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.