1. Isreal and the fact they are target #1 of Iran. Isreal can not and will not allow itself to be in a situation that an attack by Iran kills millions of Jews for obvious reasons. Isreal has most of the skin in the game here as an Iran with nukes now can put a bulls eye on Tel Aviv while funding and supplying Hamas and Hezbollah on each side and encouraging non-stop attacks against Isreal.
2. The sitting U.S. President must deal with this very harsh reality. Iran with nukes puts the U.S. 5th fleet and any garrison force of 10,000 in Kuwait at risk of a massive attack that kills 10,000 plus of our military. This is a pressure unlike even the risk of the Cuban missile crisis in the sense that even if we strike first after they get nukes, Iran could still survive a first strike and send missiles with nukes that land in less then 4 minutes...in essence a no warning nuke attack. No U.S. President could accept that clear threat to our troops stationed in the region.
3. The regional Arab states. They don't want an Iran with nukes and know it's a game changer. Now there is some balance as even Saudi has an Air Force that can strike Iran and keep them at bay. In a world with nukes in Iran on missles that now becomes a non-issue and Iran can dictate terms to all regional partners and even go after vast oil reserves in southern Iraq as well as those in Saudi and Kuwait.
4. Europe, they know Iran is far more adavanced with it's missle delivery systems and can target cities in Europe in the event they decide to attack Kuwait and Saudi for oil reserves. They can tell Germany stay out of it "or else" and mean it!
In short we have a perfect storm brewing with the location, the idiology and leadership as well as the advanced technology to deliver nukes across a large part of the populed planet. We have a country that wants these weapons for the sake of using them directly or indirectly to change the global balance of power and force a caliphate on all of us.
I contend that war with Iran is coming and I prefer we do it now as opposed to when we have an Iran with Nukes. I pose this question to you....In the spring of 1945 would Hitler have used nukes had he got them even that late in the war? The answer is London would have been the first city to ever be attacked if the Nazi's got the nuke because of idiology and that's the case here with Iran.