The US military has seldom had problems with the blowing up the enemy bit.
True however AFAIK they have never once been in this situation. Iran has spent 40+ years digging in and hunkering down. There were plenty of bunkers in WWII but this is a whole new setup, deeper under mountains, higher quality concrete assuming they knew what they were doing and dug in much deeper. To get this done in 5 days will be quite a feet. If they manage to do it I will be very impressed.
It's providing peace and stability after that happens where they tend to run into problems.
I think you are correct, what happens afterwards is usually a crap-fest. That would require a lot of boots on the ground to maintain stability for a very long time. It's not a great example but Korea is one such example. The payoff may be worth it if many of the Iranian funded terror groups are drained of resources as a result. Keeping boots on the ground for years will require funding from congress. Short of that it will just be another power vacuum filled by yet another zealot. The "if's" are doing a lot of heavy lifting in my comment.
They don't necessarily have to kill all the Iranian military, just suppress internal security enough to where the Iranian people came rise up in rebellion. It's hard for the IRGC to suppress widespread protests/rebellion if they're constantly stuck hiding in bunkers and tunnels.
I imagine that's the strategy, anyway.
I think the crap-fest bit could go better with Iran. The Iranians are closer to European in culture than many places.