My intuition about this as someone who grew up in America and has traveled internationally quite a bit is that nowhere else on earth are the middle classes so convinced that one day they will be "millionaires" than here. This causes them to act against their own best interests. (This was observed by Engels long ago: https://en.wikipedia.org/wiki/False_consciousness )
They aren't completely wrong. 76% of Americans spend a year of their life in the top 20%, 56% in the top 10%. https://www.aei.org/publication/evidence-shows-significant-i...
So I disagree, they're pretty completely wrong.