More importantly, a New Yorker and an Angeleno pay the same federal taxes.

And they can switch places without hassle: labor mobility is a big part of what makes the US currency union work.

If you have an EU passport, mobility between EU countries is a piece of cake.

> mobility between EU countries is a piece of cake.

The whole "different language" thing stands in the way of this. Plus, the Okies never had to deal with Californian "nationalism" in the 1930s, while, on the other hand, if you're Polish, Romanian or Bulgarian and you've gone to Western Europe in search of a better job you're always looked at as a foreigner, a guy who "has come to steal our jobs and destroy our identity".

On a legal level, yes. But outside of software and some other "internationalized" areas, the lack of common language makes it kind of hard

Could you explain about 20% population loss to EU in Baltic states (Lithuania, Latvia, Estonia)?

In some professions (especially construction), the workforce is already mobile inside EU. In most others, it isn't. And this is mostly due to language issues.

Actually there is Labor mobility between the States of the EU.