Oh, no doubt Obama would be finished in that case. But the damage to the country's reputation would be temendous. think about this...Iran nukes NYC. Over 1 million killed instantly on a weekday afternoon; many more soon to die. Obama refuses to retaliate after it is shown for a fact that the missile was launched by the Iranians. A battle ensues with Biden, NORAD and SAC general officers, heck even the Secret Service and Speaker Boehner are caught up in the chaos of trying to get a military response off the ground. Remember how long that took on 9/11?
By the time Obama is removed from office (after SCOTUS gets into the mix), it's the next day. Now what? Nuke Tehran? a day later. The UN and every non-ally would accuse us of war crimes. Our weakness would embolden every terrorist on Earth.
So the response would need to be
immediate, or it would have no legitimacy?
Our response to 9/11 wasn't immediate, and yes, the world accused us of war crimes. So, should we need to respond to a nuking of an American city a bit late, we do the 'American thing'...tell them to STFU and take Tehran down to glowing fused bedrock.
(Yes, it sounds crazy and vindictive. I guess I've gotten tired of the rest of the world telling us what to do.)