The US's chances of success in Iran get slimmer every year as more and more sophisticated drones and missiles come on line. It'd already be a nightmare for the US - Iranians might feel all kinds of ways about their government but they all love Iran and their heritage as Iranians and I sincerely believe they would be motivated to fight like no one the US has faced since Vietnam. Iran is a much larger and more defensible country than Iraq and the Iranians have been doing everything in their power to tailor their military to have a chance of resisting a US invasion for decades.

I think the US could destroy most of the infrastructure in the country but I think a ground war would be a meatgrinder like we haven't seen before.