The author takes PPP (Purchase Power Parity) per capita of the UK as a whole versus individual U.S. states. So what does it mean that Mississippi on average has a higher PPP than the UK? Two things:

Another way to look at it is, if wealth distribution was fair in the U.S., even people in Mississippi would be better off than the average Brit.

That’s the problem with averages vs medians. It completely overlooks wealth gap.

Here is an example. Moderna CEO made something like $500 million last year. If Moderna had 1000 employees, that would mean the company’s average employee pay is $500,000. And that’s before even adding their pay to this average.