The dangers to Israel's existence, from a nuclear-armed Iran, are real. Equally real are the dangers of a pre-emptive military attack on Iran. Perhaps the greatest danger to Israel, however, is Prime Minister Netanyahu.
America is Israel's most important ally, providing financial (~$3 billion/year), military, and diplomatic support. In response to the Iranian nuclear threat, the U.S. has been the main sponsor and supporter of sanctions against Iran. Yet Netanyahu seems determined to reduce this vital relationship to rubble by the time he leaves office.
Israel is about the size of New Jersey with a population of 7.6 million people. It's only about 10 miles wide at its narrowest point. A surprise nuclear attack on Israel by Iran, combined with a ground attack from Gaza and the West Bank, could potentially cause a second holocaust. Iran's leaders have openly threatened Israel with genocide.
Further, Iran's possession of nuclear weapons could ignite a regional nuclear arms race with Egypt, Jordan, Saudi Arabia, Turkey, and/or the UAE. Nuclear weapons proliferation in the Middle East vastly increases the likelihood an unstable non-state actor (e.g., al-Qaeda, Hamas, Hezbollah) will acquire nuclear weapons. All these possibilities are bad for world peace, and bad for Israel. Netanyahu is demanding commitments to a pre-emptive attack on Iran's nuclear weapons program in the near future, unless Iran gives up its nuclear ambitions.