Will they then expect the reverse to happen; that if someone uses a nuclear device in the U.S., we'll obliterate Iran?
If Al Qaeda does use nukes, what would our excuse be for nuking Iran, Mecca or Damascus? The best we could do is nuke what we think is Al Qaeda's hideout...which is in Pakistan.
If we get it, we won't be able to do a damn thing that we haven't done already.
If someone uses a nuclear device on the U.S., we won't wait to investigate and gather evidence concerning who the culprit is, we'll shoot first and ask questions later! Iran will be a smoking radioactive pit!
No, they'll think we'll go to the UN on our hands and knees.