Chesterton said it well in The Spice of Life:
The man who forgets nationality instantly becomes less human and less European. He seems somehow to have turned into a walking abstraction, a resolution of some committee, a programme of some political movement, and to be by some unmistakable transformation, striking chill like the touch of a fish, less of a living man. The European man is a man through his patriotism and the particular civilization of his people. The cosmopolitan is not a European, still less a good European. He is a traveller in Europe, as if he were a tourist from the moon. In other words, what has happened is this; that for good or evil, European history has produced European nations by a European process; they are the organs of the organic life of our race, at least in recent times; and unless we receive our natural European inheritance through those natural organs, we do not really receive it at all. We receive something else; a priggish and provincial abstraction, invented by a few modern and more or less ignorant men.
I do not believe the EU will last any substantial time, because all that I have seen or heard points to it being the work of "cosmopolitan man" rather than an organic cultural growth. The Greeks seem to feel no need to sacrifice for the benefit of the Poles, nor the French for the English. The elites with whom I work are happy to work together, since it benefits us all, but (as recent months remind us) life doesn't promise us desk jobs and eternally good salaries. I sense no glue to hold people together in hard times.
I'd be happy to be wrong, but I don't think I am.