Put yourself in the other man's flip flops. The degree of paranoia in the cleric's "elite" Islamic regime in Iran has never been higher.
It is good practice to keep them guessing on whether the US, or more likely Israel, will or won't go in because only the big stick will keep the dialogue with Europe open. If Iran starts rattling the sabre again as Saddam did, then it will be a stupid miscalculation. The US is quite entitled to extract payback on this clerical mafia who held the US Embassy staff hostage in 1979 in the face of international condemnation since it was then that the Iranian sponsored Islamic terror campaign began in earnest. Had the US Marines been ordered to defend the Embassy by the politicos instead of capitulating to the mob, then the US would have not been humiliated by a gaggle of zealots. This humiliation, more than anything, has led to the current situation because the Mad Mullah's regime has believed - up until recently - that the Vietnam experience and political correctness had emasculated the Americans.
They know that their export of terrorism has been rumbled and the Iranian people are highly (but of necessity very quietly) critical of the total incompetence and corruption of their so called Government.