The real threat that Iran poses to Israel is that Iran and the US may start to get along, thus undermining Israel's strategic value to the US and creating an obstacle to Israel's regional ambitions. Promoting emnity between the US and Iran also gives the pro-Israeli lobby a reason to exist, even though it is contrary to broader US interests.
By now you're quite familar with the standard trope in which Iran, the crazed fundamentalist regime, is supposedly seeking nuclear weapons in order to pose an 'existential' threat to Israel.
