The creation of the Euro had nothing to do with economics. It was all about the Euro elite taking away sovereignity from the member states. Europe was and is a poor candidate for a monetary union.
I believe you are right and we are about to find out.
For the reasons I gave, it seems to me to be impossible for the other members of the European Union to let Greece and/or Spain fail. They could, of course, just continue pouring money down Greek and Spanish rat holes. But if not, there is only one alternative: take fiscal control of the Greek and Spanish government spending. That is, of course, the ultimate sacrifice of sovereignty. Will it happen? It will be interesting to see. The Euro-weenies have two bad choices, the rat hole approach or fiscal invasion of Greece and Spain. Which will they choose? Get out the popcorn.