Maybe, but not really, obviously any one individual can have high variance. On a macro level though it's pretty easy to identify trends. The most ambitious European devs will come to America to get the much high salaries. The hiring standards for EU devs are considerably relaxed because of the reduced salary requirements. As a result many of the actively employed EU devs would be in a lesser role than their equally skilled American counterparts which results in the reduced metrics.

It's certainly not something any one individual should take personally.