A far greater scenario exist than Iran getting the bomb and their new leader seems to be backtracking on their quest for the bomb.
Pakistan has 100 nuclear weapons currently in their arsenal and they are anything but stable or an ally if the US or the West.
They play a constant shell game with their devices in which they claim that the weapons are in component state with the critical components being kept and moved separately.
However recent reports say that the devices aren't moved separately but together. Also rather than moving them under guard they are carted about in plain cargo vans with at most 2 or 3 lightly armed guards. They rely on nobody knowing that the vans are carrying anything of great value. They actually are, supposedly, far more worried about the US or NATO knowing the locations of the weapons rather than having the Taliban, Al Qaeda or other extreme get ahold of them.
Given the instability of Pakistan in general and the level of corruption and infiltration of their highest security it would be comparatively easy for one or more of these weapons to fall into the hands of someone crazy enough to use them.
As to the end of society?
US society has fallen tremendously since the 60s & 70s and seems to be in an ever steeper dive into oblivion. The same is true of most of the Western 1st world.
The Middle East is going through the growing pains one would expect since WWII when the great British and French empires dissolved. The US would have done far better to have stayed out of the ME picture. We have been far more a force of evil than good. We have sewn seeds that we are already regretting and will regret more in the future.
We could wise up and get out now and stop bankrupting America but we won't. We learned nothing from history and we continue to plunge into one debacle after another. Syria is the latest and we are showing absolutely no plan to follow an intelligent path. Instead we are aiding the very extremist that have sworn our total destruction as their primary goal.
Meanwhile some other countries have gotten better over the same time. China which was frozen in time from 1946-1979 under Mao has woken and is making great strides for their people. South Korea has grown as much as North Korea has shrunk into madness.
All of this matter very little since the planet is going into a full scale crash that isn't likely to slow let alone stop. Nature will stop the population explosion no matter what we do. But we may be the means used.