Nuking Israel would invite reprisals from Israel's own nuclear arsenal; no need to involve any other nation. Pakistan and India have also been coexisting despite their...past history, as well. I do recall the president's comments that Israel should have been carved out of Germany, too, and that the Holocaust never happened, but I didn't know about the power-grab. I wouldn't mind, though, if he took it from the mullahs and stuck it back into the democratic government where it belongs, but somehow, given the way you're saying it, it doesn't sound like it'll be democratic for long after, either.
Besides, Pakistan is just as much a threat as Iran, if not more so thanks to the questionable loyalties of its army, which is tasked with protection of its arsenal. For that matter, it already has nukes. Iran is, comparatively speaking, a stable nation, not quite prosperous, but not on the bottom tier thanks to its own oil industry. The only difference is that Pakistan's leadership has been loud and vocal in pronouncing their friendship to America, and shooting your allies (like Saudi Arabia, another nominal ally of America) sets a rather bad precedent, and makes your other allies a bit jumpy.
