Practically? Yes.

At one time it was a practical necessity to belong to some religion or other.

Having no citizenship is pretty serious problem.

Just because everyone believes you need one. But does that pass the PKD test?

Most countries are actually very stable, peaceful, and trusting. More so now then at any other time in history.

Does that prove that nationalism is good...or that its one the way out? Europe went through a period of religious bloodshed...followed by an era of religious tolerance...followed by a period of irreligion. SWIM?

Other kinds of political organization may be feasible, and that's fine, but this one is working pretty well

Nations solve the problems created by nations. Up to a point. Does religion "work" when there is a respite in the slaughter?

and changing things would probably result in trouble.

Maybe things are chainging anyway. I'm a citizen of England, and the Uk, and the EU. If you are a Usian, you are also in a federated superstate.

In any case you don't have to believe in (qua approve of) something just because you believe in (qua note the existence of) it.