Hopefully we never have to find out.Uh, no. The terrain makes an invasion a staggeringly difficult endeavor. Iraq is flat desert connected by highways. Iran is on a natural plateau, with all ground travel done through natural chokepoints.
Their army is well equipped, trained, and experienced. With a national population of 80 million. Nearly three times that of Iraq. And a modern army size of 650 thousand.
The US Would win, but it would be pointlessly bloody and a international embarrassment.