[Niall Ferguson is a Harvard professor and Newsweek columnist.]

You remember Agatha Christie’s classic whodunit Murder on the Orient Express? The problem for the great Belgian sleuth Hercule Poirot was that there were far too many suspects. The strange death of the European Union may prove to be a rather similar case.

So used are we to hearing the process of European integration likened to an unstoppable train that we discount the idea it could ever stop in its tracks. Yet the reality is that Europe has been quietly disintegrating for some time.

Outwardly, it’s true, Europe’s leaders still appear to be inching toward their long-cherished goal of “ever closer union.” Last month they agreed to set up a new European Stability Mechanism to deal with future financial crises. It’s still a long way from being the United States of Europe, but most Americans assume that’s the ultimate destination: a truly federal system like their own. Think again. Not only has the economic crisis blown holes in the finances of nearly all EU states, it has also revealed a deep reluctance on the part of those least affected to bail out the hardest hit...