Nobody would actually launch a nuclear attack against Israel in response, though. Beyond the aforementioned infiltration of major world governments by the Israelis (which would likely derail any legitimate effort to get a launch planned, authorized and executed), Israel is infamous for its "Samson Option" doctrine -- if they ever reach the point where they feel they're facing extinction (an inbound nuke would certainly qualify), they'll pre-emptively launch all their weapons simultaneously at as many global targets as possible. It's their flavor of the mutually-assured destruction doctrine.
For better or ill, they're a wily bunch and they've gotten their claws buried pretty deep into the world's halls of power. That gives them a second Iron Dome of sorts on the world stage.