We've been doing fine championing our nationalism instead of creating a strong internal market.
Because Hungarians decide in Hungary and Spaniards in Spain doing business across Europe is still very tough.
So to transport anything from Austria to Hungary you need to fill all the kind of paperwork and find the appropriate codes. And to sell it, even more complicated. And taxation? Don't get me started.
And it doesn't help most of our economies are all export economies, which is a broken economic model where you just keep hemorraging stuff and your people stays relatively poor.