If Iran were insane enough to attack the USA with a nuke, it would be annhilated in revenge. At least 500 warheads would be dispatched to Iran. Result: No such place any more.
But Iran would never do that. Why? Simple. The mullahs enjoy sitting in their palaces, drinking tea and screwing their whores (whoops, I mean "wives for a single night"). They only send stupid believers to carry out suicide missions. They NEVER take risks themselves.
