Sorry not to get back to you today, but Mother Nature decided to hand me a bit of work. Three large trees in my yard were felled by a possible tornado on Saturday while I was out of town. Thankfully, no damage was done to my house. Instead, I am left with a bunch of branches and trunks to take a chainsaw to and haul away. Thus, rather than enjoying a stimulating historical discussion, I got to be Paul Bunyon for the day.
In regards to your question about America's wealth, could you clarify something? Are you asking about our overall GDP, or per capita? If it is per capita, then the previous responses pointing to American exeptionalism beliefs would serve as a good starting point. For a contemporary treatment of that topic, I am sure you are aware of the writings of Alexis de Tocqueville.
If you are talking GDP, it will require a longer explanation.