North Korea unfortunately has given them a path forward. If you're willing to murder your own citizens en masse, you can get away with about anything.
Invading Iran would be difficult, but totally destroying IRGC and military (as long as they side with the former) wouldn't be that hard. Dropping communications equipment and weapons to Iranian opposition groups wouldn't be hard either.
The IRGC and military are HUGE. This is a numbers thing, not a competence thing. Neither the US or Israel has the munitions to make a lasting dent with air power alone.