The Euro is generally a good idea.

Like the dollar, you have a vast territory, very different economic situations in every single state, but a dollar that works well.

Whats the difference to Europe ?

1) we have no political integration
2) no common financial / budget policies
3) no means to handle a bancruptcy of a state like Greece

The problem is what ?

The southern states do not want to integrate, because lying closer to the northern country center, which is very heavy, means you loose power.

The northern states do not want eurobonds (eurobonds would mean kicking the can further down the road btw).

Game over. Exit.