Paul Krugman gets it

What has happened, it turns out, is that by going on the euro, Spain and Italy in effect reduced themselves to the status of third-world countries that have to borrow in someone else’s currency, with all the loss of flexibility that implies. In particular, since euro-area countries can’t print money even in an emergency, they’re subject to funding disruptions in a way that nations that kept their own currencies aren’t — and the result is what you see right now. America, which borrows in dollars, doesn’t have that problem.

Paul Krugman, Legends of the Fail

It’s as simple as that.

currenciesEuropeItalysovereign debt crisissovereigntySpain