Stephen Pimpare, an author and professor at UNH, addresses the issue in today's Washington Post. He disagrees with our basic assumptions - the US is a land of opportunity, where upward mobility is readily available and hard work gets you ahead.
As evidence of the weakness of "the land of opportunity" argument he notes that the rates of intergenerational income mobility are higher in France, Spain, Germany, Canada, Japan, New Zealand and other countries in the world than they are here in the United States. And that mobility is in further decline here, an indicator of the falling fortunes not just of poor and low-income Americans, but of middle-class ones, too. Poverty here is widespread. According to the Census Bureau, over a three-year period, about one-third of all U.S. residents slip below the poverty line at least once for two months or more.
Poverty is common here in his opinion "because of low wages or lack of jobs, the poor quality of too many schools, the dearth of marriageable males in poor black communities or the high cost of birth control and day care. Never mind the fact that the largest group of poor people in the United States are children. Never mind the grim reality that most American adults who are poor are not poor from lack of effort but despite it."
Personally, I think we succeed here initially because of chance, the most important aspect of which is that we were born here and the elderly among us grew up in largely strong economies.