Considering you're American, on what information do you base your opinion that it will be hard for Europeans to feel European rather than German, French, Italian...? I presume your statement about Californians and New Jerseyans is based on personal esperience?

Take a country like Spain, of which Cánovas del Castillo, one of the most influential politicians of the 19th century and several times Prime Minister said in the Spanish Parliament that "Spanish is he who cannot be anything else". It shouldn't be too hard to substitute a European identity for a Spanish identity.

I found a 2004 Spanish survey on attitudes to the EU. Out of a sample of 2488 people,
6.9% feel primarily European
27.0% feel equally Spanish and European
59.3% feel primarily Spanish
6.0% feel neither [these would be people who feel more a part of their region than Spanish or European]

In other words, European sentiment is already stronger than nationalistic sentiment within Spain.

The question you have to ask is what makes each European European, because the resons why a Spaniard and a Finn feel European are likely to be different different, but that doesn't prevent each from saying they feel European.

I am Spanish. I feel European. I don't like identity politics. Therefore, I am not particularly interested in 1) picking apart the reasons why I feel European; 2) telling the world that my way of feeling European is the way Europeans should feel; 3) passing judgement on why or how Americans feel American.

We have met the enemy, and he is us — Pogo