You can't take these things at face value.. obviously Iran is a bigger threat to "world peace" in reality, but figuratively speaking saying America can be construed as the biggest threat with its world tour war on terror threatening to visit any country that America takes a disliking to.

You could argue that America just sitting back and leaving alone would make a more peaceful world, but equally you can argue that that would allow the "rogue nations" - as decided by ze yankees - to become a bigger threat..and so on..