I was trying to post earlier, but got torn away from the computer too often to make for a proper reply at the time. And there's been an awful lot more said since the point I was going to join in, but... well, let's just say what I was going to say (even though I'm probably largely ninjaed and counter-ninjaed, in turn).
As a UK resident, us British are insular. Literally, in fact, but also (in general) psychologically/politically. For this reason we've been reluctant to go in at the deep end with "the big experiment", and what we see from the shallow end (or even from the benching at the side of the pool) doesn't seem to have given us much reason to jump in. (It's possible that De Gaul did us a big favour even
after the war.)
The fact that our own "United" Kingdom always has a few voices about partial breakaways (with or without EU participation by the splintered entity) probably isn't too relevant, but the overall feeling of historic sovereignty (at whatever scale) is surely felt at some level by individual nations. Ok, so historically borders are different and wibbly-wobbly on mainland Europe, and there's the old joke about people who have been in seven different countries and yet never left <city name> in their life. But you have a lot of old powers in Europe, with at least a perceived history and heritage and legacy, whether that be the long time-scale that Greece could (conceivably) posit to the relatively modern nation of Germany. (Both of these, and many of the others, have bumps in their progression and 'more convenient to forget' interim periods, of course, but still. And England/Britain isn't immune to stuff like the Interregnum/Protectorate.)
The recent (and ongoing) financial situation shows one thing, and that's that the half-knit financial currency system of the Euro causes problems of some nations dragging others. Either down or along, depending on your POV. Conceivably, this might lead to a hardening of the Eurozone into a truly centralised system, but it could also supernova, shedding the 'shell' countries while solidifying those that are left into a Neutron Star-like core of now solidified nations... But somehow I don't see that happening, and if there's any fragmentation it'll be more like a popped balloon, where you find fragments of rubber/latex all over the dance-floor.
As well as financially disparate, the EU is still too linguistically, culturally and 'attitudinally' disparate, I think. It's hard to tell from the outskirts I live in (and one in which our linguistic aspirations, admittedly, are far too unambitious), but while I think the average Frenchman is happy to drive into France, and the Germans are somewhat more welcome in various neighbouring-countries (and beyond) than they might have been a few decades before, can they meld?
My answer? The EU can work as a group much as the Benelux works as a group, but not since the unification of Germany (and/or Italy's own nation-state merging) has there been any actual "single-nationing" built up of old-world-orders.
The US is an interesting contrast, but don't forget that the (majority of the) inhabitants of the fledgling and later United States were immigrants, rejecting (or feeling rejected by) their Old World origins feeling more (though not necessarily
perfect) amicability with their fellow (and sometimes historically rivalric) colonists than with their original nations. And once you got beyond the first generation and (real or imagined) felt cast off, rejected or downright unappreciated and put-upon by their original country/colonial power, you've got more far more reason to Federalise an otherwise 'unowned' nation that the EU ever did.
I think there's only one way the EU could unify. By force. Perhaps of personality (and suitable opportunity) by a single leader. It's hard to think of a non-conflict way of this happening. The archetypes are the likes of Ghengiz Kahn, Qin Shi Huang, to some extent Shaka Zulu, various native South American civilisation leaders (at various points in history), the more successful individuals going by the name Napoleon, ditto with the Caesars and their ilk, most of the guys with "The Great" as a title, maybe Saladin, (some of) the Pharoahs, etc, etc... Did any of these
not create their respective superstates
without force of arms?
Of course, the world is different these days. I'm not sure if global communications and individual senses of entitlement can work for or
against the complete merging of the EU (or significant parts of it) into a superstate of its own. My own musings tend to actually go towards the scenarios envisaged in the world of Snow Crash or Diamond Age (both Neal Stephenson novels of (arguably sequential) futures where states of
any size matter less and less).
Indeed, prior to the whole Greece,
et al, situation, my personal musings were along the lines of how the EU would
break up, after an attempt to better merge... These rested mainly upon the concept of a local area (a county/'department'/stat/whatever, or an even smaller area, perhaps a city or city-equivalent area of countryside) in which there's disaffection with how the Great Experiment went, local people (perhaps including a "local regiment", of what was once a segment of the Bundeswher[1], Armée de Terre, Esercito Italiano or whatever) demand to break out of the system that appears to be unfair to them starts a process of increased renationalisation (whether initially successful themselves, or not) and "does a Yugoslavia", post Tito.
So... what was the OP question again? Sorry, I covered a lot of mental ground in-between originally trying to reply and now, so not quite sure (without spawning off another tab to go and check what it actually
says), but if it was "Will the EU become the USofE?", then I think I say no. But if it
does, it won't be the whole of what is currently the EU. And yet if it
is, it won't survive that long. If it does, then I'm a
dutchman[2] euroman.
[1] Although I think German federal states don't have their own regional regiments, these days, but YGTI. Other errors may exist in this post, through unfamiliarity with national situations like this. You'll probably have to take this for granted and work around such apparent misconceptions in what I write.
[2] I'll just speak English with a "heavy cold" accent, sing-songy rhythm and a word order and sentential structure consisting of much strangeness!