This is chiefly a social and political issue and problem rather than an economic one. The economic arrangements were supposed to lead to greater social and political unity, but that was a foolish assumption given the context. In the end, the economic context is exacerbating the social and political context.
BTW, on a similar note, the expansion of NATO eastward is another foolish attempt to unite Europe politically by creating an enemy of Russia. NATO is adding tiny states in Eastern Europe that are in the Russian sphere of influence historically, supposedly to deter Russian aggression.
No one in their right mind thinks that NATO is going to go to war with Russia over these tiny states that don't figure into anyone national interest. This is clearly a ploy to unite Europe under Atlanticism and it will also fail because none of the chief members of the alliance is willing to pony up for these smaller states which are traditionally economically dependent on Russia. It is also going to be a monster failure.
Gexit: The Case for Germany Leaving the Euro