I sense a bit of sarcasm here. If not, keep in mind that only about 4% of Europeans consider themselves "European" first. The rest think of themselves as "French," "German," "Irish," "Italian," etc. European nations do still survive, in spite of their governments attempts to destroy the nation-state. And that is precisely why the envisioned "United States of Europe" will never come to pass. The EU will die. It is not a matter of "if," but "when."
On the Balkans specifically, it would help to remember that the whole Land of the South Slavs ("Yugoslavia") WAS united under one banner, and it ended up splitting up. That is exactly what will happen if Europe tries to melt itself together completely.
Europe is giving its regions great autonomy (Scotland et al), and of course Czechoslovakia self rendered peacefully. Nobody cares there about borders within the EU, there is free movement of peoples in the EU (the Krauts are moving back into the Sudetenland), and many decisions now are made centrally in the EU.
I am glad that Serbian Americans are starting to organize. It was about time.