Except that recent statistical evidence for social mobility fails to support that statement:
http://en.wikipedia.org/wiki/Socio-economic_mobility_in_the_United_States
"At least five large studies in recent years have found the United States to be less mobile than comparable nations. A project led by Markus Jantti, an economist at a Swedish university, found that 42 percent of American men raised in the bottom fifth of incomes stay there as adults. That shows a level of persistent disadvantage much higher than in Denmark (25 percent) and Britain (30 percent) a country famous for its class constraints.[13] Meanwhile, just 8 percent of American men at the bottom rose to the top fifth. That compares with 12 percent of the British and 14 percent of the Danes. Despite frequent references to the United States as a classless society, about 62 percent of Americans (male and female) raised in the top fifth of incomes stay in the top two-fifths, according to research by the Economic Mobility Project of the Pew Charitable Trusts. Similarly, 65 percent born in the bottom fifth stay in the bottom two-fifths."
And that well-known journal of left-wing ideology "The Economist" had this to say:
"...evidence from social scientists suggests that American society is much `stickier` than most Americans assume. ... would-be Horatio Algers are finding it no easier to climb from rags to riches, while the children of the privileged have a greater chance of staying at the top of the social heap. The United States risks calcifying into a European-style class-based society."
