Neighboring EU countries are not, and will never be, nearly as much alike as are US states. This remains true even with the bitterest political and demographic balkanization in America. There is only one official language, only two functional languages, in the USA. Imagine if we had to deal with a distinct language and culture for each state. That the EU “works” in any sense is rather bemusing.
but this builds certain capabilities that come in handy while globalizing our economy.