The EU shouldn't become the US. EU countries are sovereign, with the practical right to completely ignore what the EU tells them to do, and this is a good thing for now. If an EU country legalizes weed, federal troopers do not march in, arrest all the weed dispensary owners and march them to federal prison because those things don't exist.
Ok but you have to accept that means an EU country works with a hand tied behind its back.
In the US I can start a company and instantly have a market of 350M. Start a company in an EU country, then try to expand to another country, it’s a nightmare. That company will have a lower upper bound on market size.
The EU might be a success in coordinating on regional issues, but I don’t think it’s yet an asset to the European economy.