Pray..
The issue for Chump is not Russia, nor Iran, both who are weakened, but what the other Islamic states in the region will do. I am not sure the Islamic alliances to the US in the region would survive well an attack by the US on an Islamic regme regardless of tribal differences. And Kuwait, Saudi, etc, are quite important to the US.
The difference between Iraq is that Iran is turning on itself, not its neighbours. This is a sovereign issue as opposed to a regional conflict.