The biggest problem of the EU is that the member nations have soooo different cultures and local problems.
In the USA all the states have a very similar culture and the difference between Idaho, California and Alabama is much much smaller then the difference between Sweden, UK and Greece.
Imho europe would have been much stronger if it would have consisted of the following unions that had a trade agreement.
Nordic Union (Sweden, Danemark, Norway, Finland, Iceland, Latvia, Estonia)
Central European Union (Germany, Luxenburg, Austria, Poland, Czech Rep, Hungary, Lituania).
Mediteranian Union (Portugal, France, Spain, Italy, Greece)
Atlantic Union (UK, Ireland, Netherlands, Belgium)
These four unions are much closer in cultur and regional issues and would have much easier time working in the same direction.
Then a financial trade union between these four unions and thats it.
Tex