Let´s imagine that after a joint US-Israeli air strike against Iran´s nuclear facilities Iran would then attack US troops in Iraq and win. What would the US government do? A third of the US army destroyed, would they accept a defeat, continue to fight conventionally, or use nuclear weapons? I bet they would use nuclear weapons. They are that crazy, and they know that they would be finished at homefront too if they would lose in the Middle East and not to lose face - even if the public in US would unite against their deranged leadership - they would have to act quickly. And only real way to do so would be to use nuclear weapons. Air strikes from carriers in the Red Sea and the island of Diego Garcia in the Indian Ocean(as Iran could take control of the Persian Gulf) would not accomplish that.