North Korea. Perhaps the only reason we focus less on North Korea than we do Iran is that we know so little about conditions in the hermit kingdom. But we do know that North Korea has nuclear weapons and that it has shared at least some of its technology with anti-U.S. regimes like Bashar al-Assad's Syria. Putting aside the staggering brutality of the North Korean regime -- hard to do for even the most hard-headed realist -- the North Korean regime often creates foreign policy crises, such as testing its missiles or picking a small fight with South Korea, to build up domestic support. Dartmouth's Jennifer Lind and I have argued that the North Korean regime can survive despite the country's poor economy, collapsing legitimacy, and god-awful political system, but the potential for serious instability or even regime collapse remains quite real. While we should worry about Iran's potential nuclear weapons threatening the United States, we should also worry about North Korea's actual nuclear weapons.
PEDRO UGARTE/AFP/Getty Images