Thanks to VeganProf for mentioning this one to me:
As I have mentioned before on this topic, this is hegemonic triumph: cultural belief in equal opportunity, a moralistic view of social inequality and social mobility, along with a refusal to generally discuss inequalities outside of these terms. Combine that with general ignorance of facts (thank you media) and overall anti-intellectualism and you have a generally ill-informed and deluded population with the corresponding disastrous public policy.
And let us not forget that, contrary to popular belief, there is less social mobility in the US than in other Western countries.
See also here on a similar topic.