The US cannot destroy Iran without destroying the Middle East and sending nuclear clouds around the world. That will not happen. The US cannot invade and occupy Iran because it failed in Iraq and Afghanistan to do just that and Iran is far bigger, far more organised and far more powerful. And if anyone attacks Iran there is only one scenario if armageddon is avoided - there will be no Israel left and Iran will have nuclear weapons within two years and so will pretty much every other country on the planet which can afford them because it will have been demonstrated yet again that only nuclear weapons stop attacks.
Western-backed Syrian rebels say kill foreign Islamic State (Reuters)
from the article: Obama: U.S. will do 'what we must' to prevent a nuclear-armed Iran