> In summary, America is good at allowing the poor to become middle class. It is less good at letting the middle class become exorbitantly rich, though not terribly so.

The common view is the opposite though: higher tax rates and lower entrepreneurship in Europe are assumed to put a damper on the middle class from amassing significant wealth. On the other hand, the US has significantly more billionaires per capita than most countries in Europe [1], and many of those are "self-made" (i.e. not generational wealth). What am I missing here?

[1] https://en.wikipedia.org/wiki/List_of_countries_by_number_of...