Heh, the funny thing is that Iran's practically now posing a greater threat than Saddam ever was. And with the catastrophical ongoings in Iraq (okay, I'm not saying if it was necessary or not, but the execution sure as hell was lousy) and not to mention that with the opposition for any kind of action by two other great nations, Russia and China (they get cheap oil, and well, THEY don't have to be afraid of the bomb, at least that much), the hands of the US Adminstration are pretty much tied.
Should they choose to break free from those bonds, this time they must know that they may be facing a bigger FUBAR than Iraq ever was. Should a naval blockade take place, it is possible that it'd uprise a Coup de Grace as monkey suggested, but more cynical person would probably think that in the best (worst) case it'd just raise even more anger towards the "Great Satan".
I'm not saying any kind of action (and preferably bloodless, please) wouldn't be possible, but it's certainly more difficult mostly thanks to their own past mistakes. I'd laugh at the irony of this situation if it wasn't so damn scary.