Two questions posed by Chinese citizens visiting the U.S, display at the world expo. The first, how did the U.S. become such a economic power, the second how has the U.S. avoided chaos and become such a technological leader given the state of its politics and culture.
The first is that the U.S. came into its own at the end of World War II. Now it had a good base of personal initiative, entrepreneurial spirit, and plentifull natural resources, but what it took it from a perfectly vibrant but unremarkable country to being "empire" was World War II. In WW II the U.S. had an excuse to build a mamoth industrial machine while every other developed country was being bombed to pieces. It was the geographic isolation of the U.S. combined with the strategic decision to build up a formidable war machine prior to entry into the war that allowed the U.S. to come out of the mess as leader of the free world. This was also helped by a flight of capital from the world to the U.S., since the U.S. was considered the safest haven for capital, this is what allowed the dollar to achieve the status of reserve currency.
What allowed the U.S. to avoid chaos and become a technological leader is a belief that change is good. Remember the U.S. is made up largely of people who left home, I am sure that there is a genetic marker for this behaivour, as for most other things, it is a country that believes in upheaval, of leaping into the unkown. There is in capitalism the concept of creative destruction, that the obsolesence of many things and their replacement is a good thing, that the crucible of conflict creates choices that offer the best alternatives. There is also the mistrust of technocrats, of people saying that such and such a thing is the determined best way to go, rather U.S. citizens would rather hammer their solutions. This isn't to herald the process, it simply is what it is, and it had a place in history in which it worked particulary well.
As for the technological advancement part the U.S. has benefitted from being a crossroads of global thought. Throughout history you find that such places are the birthplace of much advancement, wherever you have differing thoughts coming together new things will be born. But this is also a fluid situation, that is why seats of advancement move through history. A funny part of that is that while seats of advancement have typically moved through history, almost like a virus, most of humanity has been content to live life the same way generations before lived, life unchanging for hundreds of years. So while the age of rapid information exchange has created multiple areas where advancement occurs this is the exception and not the rule for the bulk of humanities existence.