Iran is in a sticky situation. One the one hand, they have limited resources to mount a meaningful strike against the US - and any retaliation they engage in has to be limited to prevent pissing us off, resulting in escalating tit-for-tat measures, which they cannot win. On the other hand, they cannot simply do nothing and look weak, especially with the amount of internal unrest going on there. They've painted themselves into an interesting corner.
I suspect we may see Iran doing the equivalent of Clinton firing cruise missiles at empty tents in Afghanistan to 'retaliate' at al Qaeda, before he left office.