Thing is, closure of either Iranian seas, won't affect fertilizer or many other items in the USA. It mostly affects the EU.

Crude oil is the only thing the USA is concerned about. Because that affects the whole world. You don't make fertilizer from crude oil.

I actually once was bagging the darn nasty stuff. Much of it was trucked directly into Mexico.

Real farmers know how to make their own fertilizer as well. They just need to diversify.