Iran is clearly the biggest geopolitical threat to not only Murica but the world as well (Eharding saying its not doesn't make him right).
China is #2, Russia #3 (though, my views on how to handle it are vastly different from how the establishment wants to deal with it. Aka i dont want WW3).
-Iran does fund insurgencies, but doesn't seem to do much else. Hard to see it as foe #1.
Gotta look at economics, too, though. If Iran wins out over the Saudis in the oil markets we will see a drastic transfer of power in the world.