[WS:] Good question.
I think the main reason is that capitalism as a system has never been seriously challenged from below in the US, or at least to the degree it had been in Europe. This is due to several factors:
1. Ideological hegemony that pro-business views, values and attitudes achieved in the US since its emergence as an independent nation. This is due to the fact that unlike Europe, the key institution providing structure to society was linked to business rather than to monarchy (as it was the case of Europe) and thus the business class (plantation and business owners) rather than state officials (or monarchs) were seen as purveyors and guardians of "public interests."
2. Weakness of the working class due to its internal divisions by racial, ethnic, religious, and geographical (North/South, urban country-side) identities; this was reflected and further reinforced by the prevalent form of trade unionism geared to provide "membership benefits" (jobs, higher wages, insurance) instead of representing the working class as a whole (as aptly observed by Robert Fitch in "Solidarity for Sale").
3. Politics of patronage (aka political party machines) that coopted elements of the working class by tying them to business interests in certain jurisdictions.
4. The availability of 'free" land that provided real or imaginary opportunity for "realizing the American dream" - which dampened labor militancy.
5. Universal male suffrage that defined disfranchisement along gender rather than class lines (as it did in Europe.) Although that may be less true in the South where until the 1950s Black suffrage was a legal fiction regardless - disfranchisement there was defined by racial divisions rather than socio-economic class (as in most European countries.)
As a result, capitalism as a system has never been seriously challenged from below and its negative effects were blamed on personal rather than systemic factors (bad "moral character," laziness, lack of skills, foreigners, corrupted politicians, dishonest businessmen, etc.)
Having said that, however, the US state managed to step up to the plate to save capitalism from the excessed of individual capitalists when it faced a serious systemic challenge during the Great depression. The FDR administration instituted limited social programs similar to those developed in European welfare state, which were essentially forced down the throats of the reluctant capitalists. Another instance of state intervention to save capitalism as a system is the Great Society programs instituted to diffuse racial tensions.
But these two developments only serve as counterexamples to the general rule that capitalism as a system had it much easier in America than in Europe due to general absence of serious challenges from below. When these challenges (albeit not as serious as those in Europe) did emerge from time to time, the state was more likely to act to save capitalism as a system from excesses of individual capitalists by providing limited social protections to the lower classes - against opposition from individual capitalist interests.
A short version of this argument can be summed up as follows: US capitalists can engage in reckless and and outrageous pursuits because they feel safer than their European counterparts. And they feel safer because the plurality (if not the majority) of the US population sucks up to business big time, and grunts fight amongst themselves over bones thrown to them by their business masters instead of challenging the system.
Wojtek