The Euro project has basically demonstrated that a common currency ia not possible sustainably without an fiscal union - ie. Willingness to underwrite each othe

The Euro project has basically demonstrated that a common currency ia not possible sustainably without an fiscal union - ie. Willingness to underwrite each others debt and transfer wealth from richer to poorer areas. A fiscal union requires a true political union and it is very doable given the right political stimulus - the most successful recent major example being India which unified dozens of princely states (a couple of them merged forcefully) and provinces speaking dozens of languages and having wildly different cultures into a federal political union - the unifying political stimulus being throwing out the British :-)