China and russia would be more than happy to supply the arms they need, including tanks. Both those countries mistakenly think they can contain the islamists after the west falls.
No they wouldn't. Russia has problems with the Chechens. China with the Uighurs. They aren't going to help nations trying to build a Caliphate that will empower rebels and terrorists in their own nation.
iran already has a very potent army with plenty of equipment and lots of suicidal fanatics. china, russia and france continue to supply them.
If Iran became aggressive the supply would be cut. Also even if they used their army it would be depleted long before they could conquer any appreciable amount of territory.
Just how well would this country cope with daily bombings and shootings across the nation? How long would the government continue to say the events were not terror related?
Its a different war, one like we have never fought before. They are on the offensive using a typically defensive method.
It would be hard but I doubt many would say. "I give up! I'm giving up my porno, alcohol, video games, sports and anything else good in my life and converting to Wahabism. I'll cover myself in public, pray five times a day and give up my belief in my own religion, democracy and the American way."
They can only do this with a gun in your face and to conquer a world they'd have to have it in everyone's face.
They'll never get to the point where they would be able to do this. The international community doesn't allow aggressive behavior of conquering nation states. Recall what happened when Iraq invaded Kuwait. The world will not allow Iran to seize control of Iraq or Afghanistan or Azerbaijan or anywhere else.
The most we have to fear from these people is terrorism. Not living under their Caliphate. I have as much fear of that as I do of living under Communism or a Monarchy.