Military myopia?
Big Picture:
The US has been steadily losing ground and ability to influence in the Middle East since 1979. Even when it finally unleashed that massive military it banked on, it still ended up in a worse place than before. Backing Saddam against the Mullahs created a monster. Taking that monster down (unfinished) in 1991 gave the Mullahs room to manouver at the US' expense. The 2003 invasion of Iraq might have been a display of military shock and awe, but the political muddle that followed just pulled the pants of the US. (And another leg up for the Mullahs.) Kind of kills the effect of the military display. (The US might have done what the British did in Abyssinia in the 1860's go in, smash the political structure to bits, and then bugger out asap to not get caught in the backdraft. But in this day and age that kind of naked aggression would go down even worse than an occupation.)
9/11 was the thing that seemed to buck the trend. The Iranian government ran really scared there for a while. But while Afghanistan looked like a necessary step, and a success, it's now a massive headache. And the instant international goodwill the US got over 9/11 was pissed away with unparalleled speed and comprehensiveness. (It was an instant outpouring, of doubtful solidity, but once it was there, it might have been cultivated and possibly solidified. And that certainly wasn't done.)
The US shot its wad in Iraq, and the assessment in the ME, and most of the capitals in the world, is that this final US armed response ended up a dud. The US is simply unable to do the things it claims the ability to do in the ME, and that impression is being repeatedly hammered home lately in the US waffling over the Egyptian uprising. And the fact that these days best bud Israel doesn't give a damn what the US says, unless the US says what the Israeli govt. wants to hear. (That is to say, everyone recognises that the US can feck a nation up something fierce if it sets its mind to it. It just can't do it in such a way that it brings about the kinds of happy resolutions the US maintains it wants.)
So, My What A Big Army you've got, With Knobs On, and I'm sure you know how to use it. But when, and why? Not so sure... For quite some time when the US has made a choice in the ME, it has tended to find itself stuck deeper, its influence further eroded.