Uh...if the U.S. strikes Iran, there won't be anything to hit Israel with except maybe catapulting camel feces.
Lets see all they can strike israel with is their ballistic missile which isnt a precision weapon. Their air force will be raped by the US and Israeli planes as soon as they leave Iran.
I think we'd first take out their Air Force, Navy, Silkworm batteries, and anything else that might possibly be used to interdict the world's flow of oil or attack Iran's neighbors. This may take a couple weeks, until we immobilize anything dangerous in Iran that can move.
Then we'll spend a month or two bunker-busting their nuke sites at our leisure.
Iran could easily launch strikes against Israel even if the US striked (although the Iranian strikes wouldn't be as big or as effective as they would hope).
The biggest problem for Iran would be that Israel would make Iran past tense...