I was born in a developing country and lived through a brutal civil war; and there are certainly millions of people in USA, working hard, but staying poor, whose quality of life is comparable in various categories in terms of suffering. You can fall through cracks in a very cracked system very easily. It's not like all 330mil Americans have it great.
But for the most part it’s pretty nice
How many of those 330mil would immigrate to a developing country with a brutal civil war?
Applicants vs approved, per population or absolute, documented vs undocumented, etc.
I imagine that a very large country with more liberal immigration policy will by default have more absolute immigrants than a small country with closed door policy - regardless of which one is more desirable to live.
Note further: "In 2019, with 11 percent of the United States’ population, Canada receives 32 percent of the number of legal immigrants that of the United States receives."
https://www.canadavisa.com/canada-multi-year-immigration-pla...
or finally Wikipedia, where USA isn't in the top 20 per-population immigration rate, no matter the source you check: https://en.wikipedia.org/wiki/List_of_countries_by_net_migra...
Conclusion - that statement holds minimum to no liquid water
.... The median average salary for workers in the United States is $49,764 per year.
The bottom quintile of US households made anywhere between $0 and $25,600 in 2018, with the mean being $13,258. All of these numbers are well outside “global 1%” range you quoted.
And that’s before we begin to adjust for cost of living, because you can’t just compare income without considering the cost of food, housing, health care, and transit.
Milanovic's figures do account for overall purchasing power. It would be pretty amateurish of an economist not to.
The distribution of the price level among verticals is a separate question though, and it's possible that it's suboptimally skewed in the US
Which is pretty easy to account for if one is being serious: https://en.wikipedia.org/wiki/Purchasing_power_parity