That's assuming US will have a victory.
Attacking Iran will be a watershed moment for the US, much like the attempt by the Brits and French to secure the Suez Canal from Egypt.
It'll only throw the ME into deeper chaos as Iran will activate all it's assets around and inside Saudi and Israel. US won't have an easy victory in Iran if at all.
It'll be at best pyrrhic and at worst, a humiliating stalemate.
They can and will overthrow the mullahdom or the "Islamic Republic" i.e the state, but just like Afghandistan they will be fucked with the colonization/puppet regime establishment and the insurgency afterwards.
Iran geographically, the west sits on the Zagros mountain range, to the east are two large deserts than even the Iranis avoid because it's so inhospitable, It Afghandistan but 10 times worse.
Then you have Shia Islam which has a martyrdom fetish, by which i mean a strange lub for dying for the religion, not even the typical peaceful "dying while killing lots of kaffirs", you can expect more suicide bombings or fidayeen type attacks than the usual.
And with the influence they have around the ME, you can expect Shia jihad to blossom even outside of Iran, in Iraq and other places.
And then you have the matter of Persian nationalism, I doubt they will be able to weaponize it as a force against the Shia insurgency, rather it will complement the insurgency as an anti-Imperialist component.
Iran will be the rock upon which the Great Satan will destroy himself, inshallah.