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.
This is a convenient way to frame the issue, because among other things is perpetuates the mythology of Israel as the underdog victim, facing down a sea of irrationally hostile neighbors. That's why the Israeli propagandists make a particular effort at locating and magnifying any statements from Iranian officials that they can characterize as being threatening to Israel - for example the alleged statement by Ahmadinejad (the New Hitler, we are told) about "wiping out" Israel - now thoroughly debunked but still often repeated. The mythology of Israel as the always-victim was never true of course, as even Israeli historians now acknowledge - nor is it an accurate representation of the Israel-Iran dynamics either.
The real threat to Israel: US-Iran engagement
What is the real nature of the threat that Iran poses to Israel? Is it that Iran is going to drop a nuke on Israel? No. According to Trita Parsi, author of Treacherous Alliance: The Secret Dealings of Israel, Iran, and the United States, Israel has often gotten along and cooperated with Iran when it suited their interests. In fact, when AIPAC was pushing for US sanctions laws on Iran that prohibited American companies from doing business with Iran, Israel was busy doing business with Iran through Turkey. The danger that Iran poses to Israel is not that Iran may one day decide to nuke Israel - the Iranians are not about to get into a sucidal nuclear exchange with anyone - no matter how hard the Israelis try to portray Iranians as crazed fundamentalists. Rather, the real danger posed by Iran to Israel is that Iran and the US may start to get along, leaving Israel out in the cold, threatening Israel's strategic value to the US, and posing an obstacle to Israel's domination of the Middle East. A secure, economically-stable Iran - which has the benefit of nuclear energy to power its economy in the future and is perceived as being technologically advanced - plus Iran's strategic position and relatively well-educated population of 75 million potential consumers of US goods, added to many other factors - all would pose too much of a temptation to the US to start to warm up to Iran - especially now that the Cold War is over and Israel's strategic utility to the US is severely diminished (assuming Israel was ever a strategic asset during the Cold War in the first place.)
As Trita has written,
"[I]t wasn’t Iran that turned the Israeli-Iranian cold war warm – it was Israel . . . The Israeli reversal on Iran was partially motivated by the fear that its strategic importance would diminish significantly in the post-cold war middle east if the then president (1989-97) Hashemi Rafsanjani’s outreach to the Bush Sr
administration was successful."
Israeli politicians began painting the regime in Tehran as fanatical and irrational. Clearly, they maintained, finding an accommodation with such “mad mullahs” was a non-starter. Instead, they called on the US to classify Iran, along with Saddam Hussein’s Iraq, as a rogue state that needed to be “contained.”
The Iran-Bashing Industry
Israel's characterization of Iran as an irrational threat that has to be contained rather than engaged has had the added benefit of providing a raison d'etre for the hardline pro-Israeli lobby in the US.
By 1993, with the end of the Cold War and the start of the Israeli-Palestinian peace process under Rabin, AIPAC had lost its purpose and was in a tailspin due to a series of scandals. It had essentially broken off from the Labor government in Israel over the peace process, and had alienated Bush I administration too. AIPAC's swing to the hardline Right had also alienated a good chunk of the Jewish community in the US and had raised quite a bit of ire & controversey all around: by its attempts to impose its hawkish views on the Washington Jewish Week; disclosure by the Village Voice in Aug 92 that a unit of AIPAC had investigated and harassed dovish Jewish peace groups; leaked memos of how AIPAC intended to discredit figures such as Jerome Segal of the Jewish Peace Lobby, Jim Zogby and Jesse Jackson; Rabin explicitly telling AIPAC to back off; Shamir's conflict with Bush I over loan guarantees, etc - all made worse by a series of other scandals and in-fighting which led to the resignations of top AIPAC officials like Thomas Dine, David Steiner, and Harvey Friedman... In fact in June 1993, Israeli Deputy Foreign Minister Yossi Beilin explicitly stated that AIPAC was a right-wing lobby that represented neither his government nor the views of the American Jewish public.
But then came the issue of Iran's award of a lucrative oil contract to Conoco as an opening gesture to the US. It was a Godsend to AIPAC, which rallied hard behind sanctions legislation along with Senator Alfonse D'Amato. With the election of Netanyahu and Indyk's "Dual Containment" policy in ascendance, AIPAC got back in business as never before, and they went to town over Iran, pushing harder and harder on primary then secondary sanctions legislation. Now they've gone completely overboard and are overtly embracing the likes of Rev Hagee who explicitly calls for an apocalyptic war on Iran.
In short, with the end of the Cold War and the renewal of the Palestinian-Israeli peace process, AIPAC needed a reason to exist & a "threat" to rally around - and they found Iran. As Walt & Mearsheimer have written:
In addition to this tendency for those with more extreme views to back and dominate key organizations in the lobby, there is another reason that many pro-Israeli groups have moved rightward: to keep contributions flowing in. As Waxman notes, "Many American Jewish organizations now need Israel to legitimate their own existence. Although these organizations may have been established for the purpose of enhancing and strengthening Israel, today Israel is vital for their continued viability." Portraying Israel as beleaguered and vulnerable, and issuing dire warnings about continued or growing anti-Semitism helps maintain a high level of concern among political supporters and thus helps ensure these organizations' continued existence.
And what is the natural conclusion of this sort of policy of "no engagement with Iran" ?
Although it makes good strategic sense for the United States and Iran to pursue a grand bargain, and although there is plenty of suport for that policy inside and outside of America, it is unlikely to happen anytime soon. Israel and the lobby will almost certainly try to thwart any efforts to seriously engage Iran before they get started, as they have consistently done since 1993...If the United States does launch an attack, it wll be doing so in part on Israel's behalf, and the lobby will bear significant responsibility for having pushed this dangerous policy. And it would not be in America's national interest.
So now you know.