I'm always skeptical that regime change can be accomplished by a foreign nation bombing a country's military and political infrastructure. It's never worked before. Even if a political regime is disliked by the citizens of the country, any outside force is seen as attacking THEIR COUNTRY, and they will rally to its defense!
During WWII, we bombed the German cities on a day and night basis, but it never made the people rise up and overthrow the Nazis, instead it hardened their resolve. Only their final capitulation and our occupation changed their regime.
The situation with Iran is a nightmare. We would need an invasion/occupation force of about 500,000 men--and we don't have it! Our armed forces are stretched thin already. We learned in Iraq you can't fight a war on the cheap and expect to win (as Rumsfeld thought to do). I think we would NEED many other nations involved wholeheartedly as in the first Gulf War. However, the only way I can envision such an alliance coming about now is in RESPONSE to an Iranian attack. I hate to say this but, I'm afraid either we or Israel is going to suffer the loss of a city before the world unites to destroy Iran. For now, perhaps the best thing we can do is announce that any nuclear attack by Iran or its surrogates, will result in our nuking the thing they hold most dear: Mecca (and of course following through if necessary)!