They wouldn't need to send ANY Iranian ships for the purpose. An old junky freighter could do the job.
As far as retaliation is concerned, sure, our military, not in this country would be available for the job. The damage would still be done to this country, with regards to all things electric, or electronic. Folks wouldn't be able to survive without the steady flow of food from the trucks and trains that carry them across the country on a daily basis.
I think the Iranians are too egotistical to use just one missile. I would think they would try to barrage the whole cost for show. The USA would not let foreign oil cleanup ships in the Gulf of Mexico to clean the oil spill but I suppose they would let terrorists in.