US military force doesn't translate will into battlefields where the enemy employs assymetric warfare.  And absent airpower, the ability of the United States to project power into the region is seriously limited.

I also question whether there Iranian perspective on this doesn't see the recent uprest in the Arab World as an opening. Agree or disagree with the premise, the recent conference on the Arab Spring in Teheran suggests that the Iranians see these protesters as a potential fifth column. Attacks on Ras Tanura and oil infrastructure would allow the Iranians to punch way above their weight.  If they think that they can pull that off, it may be that they think that they can force the US to withdraw from the region.

Reality aside, perception is what motivates action.  Even if there is ultimately zero chance that they can win, the Iranians may think that they can.  That being the case, things could go to shit because of misperception.

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg