More than any other people in the world, Americans believe in going from rags to riches. The American Dream is that anyone can rise up from poverty and make a fortune.
The irony is that the United States is actually one of the harder countries to make your fortune. In Canada and Denmark, people have practically twice the odds of rising up from the bottom 20% to the top 20%. However, if you live in certain cities, like San Francisco or Seattle, your odds are close to Canada, while if you live in places like Nashville or New Orleans, your odds are much, much lower.