IMO the US is the epicentre of the cult of the individual which stresses personal pleasure and freedom over value creation in society. That's what causes it.
That doesn't jive on a historical basis when and where enlightenment era thinking and classical liberalism were much higher then they are today. Unless I am misreading your comment and you are simply talking about hedonism.
It's hedonism + individualism. We tell our children things like "you are unique, there is nobody else like you" and "just be yourself" and we ask them things like "who do you want to be when you grow up?". We raise our children to be identity driven.
Then they grow up, find a lover, and realize they need to give up parts of their individuality in order for the relationship to work.
Whaaaatt?? Give up my individuality? But I was raised to enshrine this above all else! Heck no, I'd rather divorce!
As a non-American watching U.S. culture from the outside, I generally agree that those two factors are important contributors to many problems. I would also add to hedonism and individualism the encouragement of a "just-world" myth, which comes as a corollary to the American Dream: you can achieve anything if you work hard for it—therefore, if you didn't achieve it, you didn't work hard enough.
This results in low self-worth of many people in bad circumstances, lack of compassion towards them from those who are better off, and sometimes active disdain from those who were lucky enough to climb out of poverty, as an overcompensation for their own past hardship.