How does Iran threaten our “survival”?
Look, I would favor declaring war on them (first), issuing an ultimatum over the nuke program (next) and destroying the nuke sites if not surrendered (third).
But none of that is going to happen.
The MOST they could do to us would end THEIR survival, not ours. They could nuke a few targets, yes (which is why their “death to America” is cassus bellorum), but have not the means to “threaten our survival”.
Supposedly all it would take would be 1 or more well placed nukes detonated over the US. The resulting EMP could be catostrophic. Fired from a container ship lying off the coast in international waters...