Their government is so weak that it probably wouldn't make sense for the US to intervene militarily. On the other hand, the US has used Israel to further mutual aims in Lebanon before...
This could actually provide an excellent opportunity for the US though. OPEC has been 'punishing' the US by raising gas prices, as recent US actions in the Middle East have not been to their liking. However, an Iranian power play is something that seriously worries the Gulf States that comprise OPEC's core - to the extent that they've even said they'd be under Israel's nuclear umbrella than bowing down to Iran. So, the US has a bit more of a countermeasure than before. The key now is whether that will actually get utilized properly as leverage, or if the OPEC-paid senior staffers in State etc. continue to pass such chances up.