The highest GDP per capita city in the U.S. is Washington D.C. at $150k/person. Silicon Valley is around $75k/person. Carve those jobs out and the median salary in the nation decreases, meaning a lot of the jobs across the rest of the nation are no longer classified as "low paying". NYC's metropolitan area is $65k/person for about 20,000,000 people, those sway the numbers too.
The bigger swing is on the European side, Monaco is like $160k/person, Leichtenstein $140k/person, Luxombourg @ $115k/person. If those numbers are added in, that sways Europe's numbers. Not including those is like carving out Wall Street from the U.S. data.
And I'm not sure how Norway is at $100k/person (has to be an oil boom I'm assuming). Yet they were not even listed as part of the chart. Think adding in their data isn't going to swing the numbers of Europe? It is like excluding Alaska from U.S. data.
Just combining, say, Germany and Spain's numbers, Spain suddenly has a shit-ton more of "low paying" jobs. It's like separating out Mississippi's data and analyzing it separately from California's data.
However you want to rationalize it, this is not even close to an apples-to-apples comparison between the U.S. and Europe. So much so it's not even an apples-to-oranges comparison. This is an Apples-to-Peanut Butter comparison.