The Euro nearly capsized the whole European project a couple of years ago, and many experts expect it will eventually crash and burn in another major crash (which, courtesy of Trump's reckless overheating of the US economy is likely to come within the next decade).
I am a strong supporter of the European project, though not of federalism, but sometimes the Euro-federalists are as deluded as the Brexiteers in their devotion to myth-making. The EU cannot survive without democratic legitimacy and Euro-federalism would rob the Union of that, as the member states are reduced to sub-units of a federal state where citizens in most of Europe ended up dwarfed by the dominance of the larger states. The difference with the US is that only three of the US states ever had an independent existence as a nation state and so possessed a strong sense of independent identity. All EU states have had, and citizens define themselves through that sense of national identity. In addition the US could compromise on some basic democratic principles the creating itself in the 19th century. So it could create an electoral college, an originally indirectly elected Senate elected by local state houses, etc. Those undemocratic compromises would be unacceptable to much of the nation-states of Europe in the 21st century. But without fundamentally undemocratic compromises a federal state could not get off the ground.
The EU worked because it pooled sovereignty. It didn't usurp it. Member states still had their own independent structures, independent policies, and independent legitimacy. The EU worked because it did not create a rivalry between itself and the nation-state but was complementary. The day it tries to assert its dominance and reduce the nation-state to mere US states is the day it will collapse, because millions will always pick their nation-state. It is the same way as if you ask millions what their identity is they will say "Irish", or "French", or "German", or "Polish", etc. They will define themselves as Irish people who live in Europe, or Italian people who live in Europe, not Europeans who live in Ireland, or Italy, or Poland. Those who thought national identity would wither and die and be replaced by a new European identity have been proved wrong by the resurgence of nationalism, which was often a response to a sense of an increasingly arrogant European elite.
The fact that some don't understand it in part explains their shock at Brexit. They find the desire in Britain for traditional blue passports puzzling. Yet recent polls across Europe found massive support in other countries for having their old passports back too. The passport to them isn't a technical document, but a badge of identity akin to their flag, their anthem, and their history. That sense of community identity is central to humans, and you dismiss it at your peril.
➽Jim Duffy is a writer.