I was not talking about myself. I worked in Barcelona for a while and moved to the US on 2009. Usually engineers don't have a 8-6 working schedule; in the company where I worked it was more normal a 8AM-9PM. 1h for lunch. And during deadlines it was "normal" to stay until 1-2AM. And back at 8, of course. All that for 15K. Sounds great, doesn't it? I left the job after 6 months because I considered that it was not a "good deal". It is true that I could be close to 30K in 1-2 years but...
I can't talk for all american engineers, but people that I know are close to the 100-120K without working 50+ hours. The difference on holidays is one of the biggest differences, that's true. And social benefits. As for your last comment, foreign engineers should definitely consider that!! Spain universities are pretty good (our engineering undergrads were 5 years until the current Bologna system) and engineering programs are considered really tough.