But, yeah not that we're wild about international train travel--that's a sore spot for sure. But generally we view the differences as a kind of richness and less of an inconvenience.

Unless you reach an economic moment where you can pay the same to a policeman in Sweden and a policeman in Greece there is never going to be a socioeconomic identity that would allow you to aggregate all these people in some sort of federation police force. Same for rail, same for most anything where there is a cost or expense or transaction.

The diversity of systems reflects a diversity of arbitrage. Brute forcing that into a single entity or federal body is ivory tower thinking.

I think you misunderstand the history of the EU project: its goal is what you describe, but it must be balanced with respecting the autonomy of each individual nation inside the union. It can only work if all involved governments agree to do it. Which is an incredibly difficult thing to achieve.

What we have now is the progress we have managed to make so far. If it does not appear like much, well, you should have seen what things were like before the EU, especially regarding red tape.

in general the EU strategy has been to agree common rules and standards. But there are also examples of common infrastructure, e.g. the Euro bills

it will be interesting to see how this might develop for software related to public institutions