When James Truslow Adams coined the term "American Dream" in 1931 he defined it as: "life should be better and richer and fuller for everyone, with opportunity for each according to ability or achievement".

Social mobility in the United States is better than most countries in the world but not particularly high compared to similar countries. More worrying is that it has been falling over time. This kind of social stratification eventually results in large swaths of the country and citizenry for whom life is not better and who do not have the same opportunities.

Having more money certainly helps -- it's hard for anyone to live a "better and richer and fuller" life if they cannot afford necessities. But past a certain point the correlation between a country's wealth and measures like happiness, life expectancy, social mobility, life satisfaction, etc seem to break down, especially in the US. Which to me indicates that we're probably not using our wealth efficiently.