On the US side - many (probably more than we think, but less that Israel hopes) politicians wouldn't get re-elected, and those who support Israel would be elected in their place (these guys are organized!...;) Countless agencies would be clamoring for the 3 billion/annual largess we send them. Europe, the Middle East, and the rest of the world would be a tiny bit nicer, but they still have plenty to complain about...
Several Christian groups would probably support Israel no matter what.
On the Israeli side - attacks would seriously escalate. The Arab countries can't actually go to war (Israel has nukes), but everything short of that would be a go. The UN would pass resolution after resolution declaring the existance of Israel (and probably Israelis) illegal, and they'd all pass. With no support (we're the only ally they have), I think you'd see what few Muslim countries that do recognize Israel, would recall their ambassadors. Israel would be hopping mad at us, and I wouldn't be surprised if they turned on us, the same way Iran turned on us (to be honest, Iran never liked us anyways...
. I wouldn't want to be an American in the Middle East if that happened.