Sorry, my friend...you (and Zarf) are wrong. It would be the beginning of the war....then the end, at our choice of time and place.
In a rational world, it would be the beggining of the end of Iran, as the next step we would be sending in the B-52's with Slim Pickin's at the controls. Instant parking lot.
In the new metrosexual US, Congress would demand we pull out and then try to cut the funds. And many people would support them.