There is room, always, for interpretation of the facts. I would simply point out that in the case of Florida, Alaska, etc., there was at least a common language at hand. Much of the problem with mobility of factors of production is created by a multiplicity of languages. An UK person cannot, realistically, consider relocating to - say - Greece to work and live without learning Greek to quite a sophisticated level. Cultural separations become easier to overcome (indeed, they can quickly become "quirky" or "charming"), provided they can be explained or described efficiently through a common language.
On the currency matter, with local sovereign currencies the ability to re-balance through currency depreciation helps a great deal to limit the levels of austerity required.
The EU has evolved from a free trade area to a more federal proposition. This is partly the cause of the antipathy from some quarters. Interestingly, despite the pro Euro comments from politicians, it is widely held that if referenda were to be held in the other EU member countries there is a tangible risk that they would vote to leave the EU also. The widening gap between electorate and government across the region is worrying, and suggests that the political classes are losing the faith and support of their voters.
It is difficult to watch this playing out, without any real ability to affect the outcome. Overall I am disappointed with the UK parliament, who have behaved in a shifty manner whichever camp you support.