.... The median average salary for workers in the United States is $49,764 per year.
Which is pretty easy to account for if one is being serious: https://en.wikipedia.org/wiki/Purchasing_power_parity
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
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.