The European Union can never be viewed as a "nation" because of the vast differences in language, culture, etc. between the client states. It is ostensibly an "economic union." American nationalism based on common language, common heritage, common values, and common experiences pre-dated the Revolutionary War.
In my example, you will never find anywhere where I have said that the European Union is analogous to the pre-Civil War United States. My example was a hypothetical set 20 years into the future.
For one thing, the European Union Constitution has yet to be signed. As you know, that latest fly in the E.U. Constitutional ointment is the issue of voting weight between large and small States. Spain and Poland are now fighting to keep more voting weight for small States and France and Germany are fighting to have less voting weight for the small States. An identical issue arose and was dealt with at the U.S. Constitution Convention.
American Colonial heritage may have been formed in common experiences during the Revolutionary War but, likewise, European Union heritage has been formed in the shared tragedy of the suffering of World War II and the Cold War.
In regards to "shared experiences prior to the American Revolutionary War", that was made up, to a great extent of escaping the religious persecutions of earlier generations with Puritan New England and the Cavalier South coming from opposite ends of that spectrum.
In regards to shared "culture", New England culture was based on a Puritanical, maritime and then industrial free-labor society while the Southern culture was based on a Cavalier, agrarian, slave-labor society. That is a vast cultural gulf that will not be found today between, say, Spain and Germany.
Although it is true that the European Union is, at the current momement, more of an economic union than a political union, it is their stated goal to form a political union. That goal took a Spanish and a Polish torpedo to the port side earlier this month but both France and Germany are determined to keep trying to achieve a political European Union nation-state with, of course, Germany and France as the dominant entities.
As time passes, it is very plausible to see the European Union fall apart before they ever sign a Consitution but it is also very plausible to see the birth of a political European Union, complete with a Constitution ratified and signed by all members.
If such a European Union Constitution comes to pass, it may very well address all potentially catastrophic issues.
If such a European Union Constitution comes to pass, howver, it may also very well repeat the grave error of the U.S. Consitutional Convention where elephants such as the incompatibility of a slave-based culture and a free-labor based culture and the entire issue of the legality of seccession were swept under the rug so that future American generations, say, in the 1850's, 1860's or 1870's could peacefully resolve those issues that nobody wanted to hash out, once and for all, in 1787.