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As the United States heads into a crucial presidential election in November, it must keep a wary eye beyond its borders. Will there be a conflagration - of either an economic or military kind - that might consume the world?

China, the United States’ chief rival as a superpower in the coming decades, is also facing a potential leadership change this year. Though the U.S. has pulled out of Iraq, embers of conflict continue to burn brightly in Afghanistan and Pakistan. And the Middle East, with Iran’s unceasing bellicose posturing and the Arab Spring’s unsettled affairs, will continue to be a flashpoint.

But the world might be plunged into more disorder by not just guns and missiles. The Eurozone crisis could cause the disintegration...