I don't think US air strikes on Iranian miltary targets would help in regards to getting rid of the mullahs. All it will do is give the mullahs another excuse for a major crackdown.

I think it's instructive to look at invasion of Iraq. I think the timing and the decision was strongly influenced by the French and their campaigning to avoid the invasion from happenning. In other words, like all war, it is caused by a failure of dipolmacy. Had the French govt not threaten the veto and instead had been in the American corner, the Iraqi invasion may not have occurred. The French in there vast stupidity, shutdown to avenue of growing international political pressure to make Saddam Hussien comply with cease fire agreement. Faced with this road block, invading Iraq in shortest period of time, became the best option. Remember that Turkey wanted and wants to become a EU member, in terms national interest this is much more important to them than other issues.
So basically the French gave Saddam Hussien hope and the French didn't think America would pull the trigger and thought it would be a serious political disadvantage if the US did this, for French politicans it seemed like a win-win situation. Had the French not opposed, it probably would have resulted in coalition forces being potentially launched from Kuwait and Turkey. And Saddam Hussien would not have had any hope.

No US president wants to use miltary force, not if there is some other solution. Now, that the French are aware that the US are bunch of friggin cowboys, they probably will not make the same mistake for at least a decade or two. So the Iranian matter is being and probably will be resolve by politican means. With international pressure the mullahs will be forced to cave.
It's really quite simple, Iran depends upon oil export, the US [or even a puny naval power] could stop oil tankers. And if you look on a map, Iran is now surrounded in terms of land area.
So, soft power backed by the potential of hard power is all that's is required.
Finally they is no political advantage to nuke Israel. The problem isn't that Iran would directly use nukes, but that some faction of Iranian leadership will use nukes- assuming they had them to use.
Nukes do have one advantage, the powers of the world do not want the leadership to lose control thereby allowing a small group which lacks political power to steal a nuclear weapon. It's sort of like a criminal threatening to kill himself- a Iranian nuke is likely to have higher probablity of being used against Iranians.