While the salaries are indeed lower, you should take into account that in the US people almost always report their salary before tax, whereas in Europe salaries

While the salaries are indeed lower, you should take into account that in the US people almost always report their salary before tax, whereas in Europe salaries are almost always reported after taxes. An engineer earning 100K in Europe will be listed as earning 60~65K, whereas in the US that engineer would be listed as earning 100K, despite earning the exact same wage.