The fact of you being oblivious that many EU state members populations feel that there are more differences than communalities with other member states, and that such a decision would require a large majority of the popular vote, in all the countries involved, to be achieved.

Even for a nation to join the EU, referendums are done for that purpose alone, much less to transform the EU into a Federation, and specially considering the current political climate, and the rise of far-right sentiment all around the world.

We are more likely to see WW3 start, than seeing a federated EU, and odds are, with a WW3, humans will no longer have the need for any federation of any sort. Maybe cockroaches will!