This is very deceptive. Under this methodology, people too poor to be called “middle class” in the US would be called middle class or higher in the other countries. Note how much higher the median income in the US is than in any other very large country (UK, Germany, France). There is no doubt the US is more unequal, but absolute wealth for the vast majority is higher.
So, what looks like a higher number (even adjusted for PPP) might still be lower in practice.