It would be a good start but as long as the US supports them they’ll remain sufficient enough that their ruling class can enjoy their standard of living. It’d be the same as turning the US into a pariah, only the poorest would suffer. Might get some of them to flip on their support for the regime since the consequences hit home, but both regimes are self-sufficient and no longer need the support of the people to maintain power. The wealth class in the US could survive a long blockade on the resources available there, natural and human, if cut off from it’s ability to outsource exploitation.

The real cost to dislodge these regimes is going to be money and blood, because they will not give up their power without a fight externally or internally. We got rid of Trump once and he unleashed his supporters on the Capitol, they’d vote/fight for the same thing the next time they got a chance. Same in Israel. It’s probably going to take a combination of external powers leveraging their global economic influence, apply military force, and coordinating with internal opposition to oust the central powers, then stick around and help what can be scavenged of the resistance to build new infrastructure and help prevent the Lost Causers from creeping back in to positions of influence and power.

Nobody wins in a nuclear war.