I think it also has a lot to do with the way Americans view failure (versus Europeans and a few Asian countries).

In America while failure is not a good thing, it is also not a permanent thing that can scar you forever as a pariah in both society and the business community. You can try again and again... I could be wrong, but I don't think this is the case for Europe or countries like Japan; it's much harder to try something entrepreneurial more than once if you failed the 1st time...

Case in point, I think it took Sam Walton over ten tries before he got it right with Walmart. (Hell look at Edison too)

(I think as Americans we're just crazier than the Europeans.)