Besides the fact that Europe does cost the countries a lot of money, people don't really support Europe here, due to the fact that they don't see added value.
I guess this is the same for the States. What is the added value besides being able to life in any state or the shared currency. People should ask what extra value a higher institution will bring.
In contrast what we think there are added values, they are just not in the plain view. Take Brittan for instance with their Brexit. Most people already regret voting for it.
Take Catalonia in Spain, where 50% of the votes were in favor of the separation but also 50% were against.
If the states will separate, probably new born states will start to co-operate after a few years!