Over the past half decade, the decline in the dollar’s value against all major foreign currencies and the concurrent rise in oil prices have put the American economy on a precarious footing. Despite the danger, changes in financial and commodity prices have been gradual enough that the economy has had time to adjust, forestalling the kind of swift, deep crisis that keeps the world’s central bankers awake at night.

We might not always be so lucky, however. As the subprime mortgage crisis shows, the global economy is more connected than ever before, and vastly more complex. What began as a slump in one segment of the U.S. housing market has spread rapidly across borders, undermining debt instruments worldwide, staggering massive financial institutions, and thus affecting areas of the global economy not directly connected to the mortgage sector. Future crises could have roots far deeper and effects much wider, thus doing far more damage to the U.S. economy.

Imagine, then, a small group of actors—none friendly to the United States—deliberately triggering an acute economic crisis at a time of their choosing. Such a scenario would constitute a strategic vulnerability of the highest order. Sadly, this scenario is not merely hypothetical.