When Iran gets nuclear weapons, and they will if unimpeded at this pace, they will shut down the Strait of Hormuz and cut off our oil and threaten us with nuclear terror if we attempt to militarily intervene. Instantly we will have to adapt to life that was lived in the 1800s but without any skills to do so. It will be chaos with a breakdown of modern civilization into one from the third world.
I believe Iran intends to use its remaining oil to power a new Islamic blitzkreig upon the western world as they create a new caliphate, which is their goal.