One thing to keep in mind is that the current Iranian govt is purely ideological, not a standard type of Government which can be replaced easily, through mock elections like done in other places. They can make any US involvement tough by turning the whole region chaotic (Hormuz, Proxies, Hizbollah, Houthis, Missiles, etc, etc). And still come out unscathed and maybe stronger.
Ariel Sharon did say (and repeated by Yair a few months back) that any dreams of changing the govt in Iran is a waste of time, militarily, it will just unite Iranians. As per him, the only way is to change the minds of Irani people through consistent propaganda. But any such propaganda has been pretty much countered by what has been happening in Gaza and now by Israeli attack. Sharon was also against this attack, saying Israel will give a new life to Iranian Govt if they do so, the more Israel gains, the more Iranians will rally around Khamenei.
So, fall of Iranian govt its not that simple either, just via the US.