Language us a powerful factor in population dynamics (see Canada with English and French) and in Europe you'd be dealing with major language roots.
English obviously, but also French, German, Spanish, Italian, Greek, Polish and so on. I don't see much cohesion with so many languages, and no current country to give up language primacy.
Using language to create an us-versus-them situation is easy, and I don't see this happy union-of-equals easily subscribing to a federated state concept.
There is a small spark of European identify slowly forming amongst younger generations, but it will take decades before anything like a federal union would even be feasable.
Not to mention the economic power difference is huge.
I really don't won't Europe to look like India in any way, administratively, politically and logistically speaking. Not to mention the countless tensions you can feel accross the country when you travel there. It seems like a ticking social bomb when I go there, and we don't have the class system to shut up lower classes and women.
Those mammoth states are only interesting for people with power ambitions, as this last war demonstrates.
The next decades will be fascinating to observe in that regard.
Do not underestimate them. But many ppl noticed already that nowadays this is not the best way to organize and that they are just there to suck resources.
But they will try with all kind of tricks to keep control, unfortunately.
In the modern high technology world, both (1) and (2) require increasingly higher investments to sustain advantage which favours bigger states. Small states have to work very hard on carrots on (2) in particular to avoid being trampled. Tax friendly small jurisdictions largely survive at the whim & fancy of the elites of the bigger countries whose private interests they serve. Tourism focused small countries face the same pressures of serving the elites of bigger countries and in fact were trampled during covid lockdowns. Small countries that can't make (2) work stay poor.
The Ukraine conflict effectively demonstrates the point. Previously, Ukraine failed at (1) in the provinces which had high ethnic Russian populations and (2) by giving up nuclear weapons and giving up Crimea without a war which enabled the invasion.
Even though it turns out Russia seems to have badly miscalculated it's ability to win, the war has dragged so long in spite of causing major global economic disruptions because no one else feels able to intervene due to the high technology Nuclear ICBM threat.
If people understand that power calls power, that too centralized power is evil and that the world is not as dangerous as they pretend (in the sense that safety is more due to conventions and culture than on surveillance everywhere) then they will start to refuse it because they will understand the threat is the state itself when it grows so much. This is my current perception but was not so like 20 years ago or 25.
I know many ppl that do not believe anymore in tax systems as an effective vehicle to solve most problems but see it more of a problem where some ppl are doing their business from.