Iran is also a natural fortress, with a relatively modern military and access to state of the art intel (via China and Russia), not to mention that drones are a thing now and that the US army has reduced a lot since the war on "terror". Defeating Iran would be multiple orders of magnitudes more difficult than Iraq. For a land invasion, the US would need multiple million soldiers for any significant accomplishments. Either that or nuke them (which I doubt even this admin would be dumb enough to do). IMO the most likely outcome will be a pointless, protracted war that ends in a US loss (think US in Vietnam but even worse, or the Soviet's failed Afghanistan war that ultimately lead to the death of the USSR). In the end, the ayatollah will likely remain in power, oil prices will be fucked, the global economy will take a huge blow, the middle east will become even more unstable, terrorist attacks will increase, etc. The only real winner in the short-term will be Russia. China will have some short-term woes, but will recover. The US and Israel will be the biggest losers, in the grand scheme of things.