There's no way anything can be achieved in Iran without at least half a million troops in the region (which Israel could easily provide, if it was to get involved directly, but they won't want an all-out war). There's no way America can come up with this many soldiers, not even if two-thirds of them speak Spanish.
If the U.S. starts bombing targets in Iran, the insurgency in Iraq and Afghanistan would multiply by twenty. The inevitable destruction of Iran's puny air and sea powers and missile launchers would be meaningless - it will be a long s guerrilla war in an area many times larger than Vietnam, and also more populous. Sealing off Iran's borders will be next to impossible, and the "westerner death toll" will go from thousands to tens of thousands.
Withdrawing will then be many times more discouraging than it is now, because it could lead to a "Greater Persia" with expanded powers in Shia Arab regions, and many more problems for Israel.