Pakistan and Iran are going to have their own hands full. Pakistan for one is about to get into another war with India and they are harboring Bin Laden. Iran has chemical weapons and would get involved (which would of course bring the US into things).
Israel may be a democracy, but they are crazy enough to fight back with nukes unfortunately. They wouldn't lose straight up to Lebanon or Palestine, even without nukes (their airforce would win it for them). It would necessitate another Islamic state getting involved, which would eventually start WW3. France is in charge of Syria and Lebanon, per the Mandate of Mesopotamia. Good ol' Britian was responsible for Iraq and Palestine lol. I would rather kill everyone in Saudi Arabia the most, to be perfectly honest. That place needs it the worst.
We all should know by now that the USA will not stay out of the Middle East. Some seem to think that politicians will change things and make us more isolationist, which I think is naive. I wish we would just sit back and watch them all kill eachother off, but that won't happen. The second someone outside of Palestine or Lebanon get into direct conflict with Israel, the majority of the UN will be involved (not just the USA).