Employment aside, there are other things that matters when you change countries / continents. As an European, I wouldn't like to move permanently to the US.
If you are making enough money in Europe, I don't see much incentives to move to US.
Sorry, as a somewhat disgruntled European I couldn’t resist.
France has one of the highest tax-to-gdp ratios in the world (46%). If you like government constraints it’s not the place to be.
Few people understand and value those feelings today, but I’m one of those few. I’m not naive enough to think that the US is full of people like me, but there are more of us over there, and it’s not socially acceptable to piss on us endlessly (as it is in Sweden I’d say).
If we would be very, very unhappy I guess we could pack and leave, but that would be a worst case scenario that I'd like to avoid for the enormous stress that it would cause.