The thing is, as a result of not being in the euro zone, the same sort of situation that Greece is in could not happen. In a way, it's really a disaster to have a monetary union without a fiscal union.

However, the main benefit of the EU is the single market, both in terms of goods locally as well as leverage for negotiating trade deals with other, non-European countries. That's going to be what hits them the hardest, because they won't get such a good deal, especially outside the EU