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.