It's not just about classical economical mechanisms. With Euro there is a large psychological and political component. It is hard to estimate indirect effects

It's not just about classical economical mechanisms. With Euro there is a large psychological and political component. It is hard to estimate indirect effects on Europe's economy (500M people, combined GDP higher than US). If you can get Europe to feel and act more as one unit, the effects could be huge, possibly dwarfing effects from differences in maneuvering space for monetary policies.