The people in the middle are still poorer in your example. The article doesn't suggest the richest Americans are poorer than the richest people in other countries.
My point still stands. I wouldn't define the "middle class" as the median salary. It's a band around the median. Throw in a couple higher salaries just above the median and a country could have a wealthier middle class, but the median is lower.
So if the distribution for the US looks like this:
$10K, $20K, $30K, $50K, $100K
And another country looks like this:
$10K, $20K, $40K, $50K, $60K
We're going to say the US is "poorer"?