Part of the reason for this is that in just about every society across recorded history, the degree of upwards mobility was much worse.
Yeah, and compared to a corpse, I'm in excellent health.
Hard facts: The essential American myth is that of unlimited upward mobility. The hard truth is that the upward mobility is a lot higher in most of Europe. Especially in those loathsome socialist, scandinavian countries.
The US is rapidly approaching the social structure of central- and south america when they were dictatorships while being in complete denial about it. Not that I care, it's fun to watch from a safe distance.