China, Russia, and others in the region would take Iran’s side if they got involved.
We’d have Saudi Arabia and Israel, probably, but our usual international allies would probably sit this one out due to their experiences in the awful bloody occupations In Afghanistan and Iraq.
Current U.S. relations with Turkey are abysmal. They wouldn’t help us and might even take Iran’s side.
The current alliance structure does not favor an aggressive war with Iran. At all. We could only “win” by carpet-bombing them with tremendous innocent human casualties and cost to our reputation.
Yes, they wouldn't help us, but they also wouldn't help Iran. In fact with our military might, some of Iran's allies like Russia and China would hesitate to get involved.
