First of all, the Israelies with take care of Iran before we have to. They don't take shit from anybody- a suicide bomber bombs a restaraunt in jerusalem, and half an hour later Israeli helicopters are launching a rocket attack. The Israelies will bomb whatever facility it is before it starts producing weapons grade plutonium just as they have several times in the past.
Second of all, Iran's military has no technology and can't hurt anybody that isn't really close to them, so people in Europe and North America have nothing to worry about.
Thirdly, what the hell is Iran thinking doing this crap when we have several hundred thousand troups on the ground right next to them? How stupid can you be?
Finally, it would be very very stupid of us to do anything more than launch a few missiles at Iran. We could destroy thier infrastucture just like we did to Iraq, but there is no way we could win an all out war including an occupation. I don't think WW3 will happen in the middle east. More likely it will involve China, but problems with China are in the extremely distant future if they are going to happen at all.