Mutual disappointment of Israelis and US Jews is almost unavoidable when there is a clash between Washington and Jerusalem. It is unavoidable as Israelis will always feel that US Jews should be "doing more" to subvert American policies, and as American Jews will always feel that Israelis keep forgetting that they are Americans first, supporters of Israel second. It is unavoidable, but not always severe when the clashes concern policies related mostly to the interests of Israel alone. The mutual disappointment becomes much more problematic when the clashes are between core interests of the two countries.
Thus, the clash over Iran might be the toughest gap ever to face these two communities of Jews.
Think about other issues that might cause friction between Israeli and American Jews:
Who is a Jew? – When this issue comes up Israel is usually willing to withdraw any new legislation proposals or initiatives which US Jews actively oppose. Pollard? –A heartbreaking story of one man that has been in prison for much too long, but his release is hardly an existential issue for Israel. Settlements? – A majority of Israelis and a majority of American Jews agree on a two state solution and in both communities most people don't have much hope for an agreement any time soon, so debates and disagreements can be pushed aside. The Western Wall? – As soon as Israel realized that this is becoming an issue that seriously damages its relations with US Jews it began taking care of it. And honestly, it is an issue that was blown out of proportion anyhow (because of Israel’s bad behavior).
Iran is different from all of the above and from all other issues of possible contention. Iran is the issue that Israel (the government and most Israelis) deems existential. It is also an issue that is truly at the top of the American agenda. When we talk about Iran we are talking about an issue at the heart of American grand strategy, not the marginal shenanigans of a State Secretary that's a little too eager to bring about peace in the Middle East. Iran is where what Israel wants might stand in contrast to what the American government wants, to what American voters want, and to what most American Jews seem to want.
Consider Syria, and see how Americans and Israelis differ in their outlook: American voters were overwhelmingly against American military action in Syria. Israelis believe that what happened in Syria was a pathetic and worrying demonstration of a lack of American resolve. In other words: Americans want minimal or less involvement in the Middle East, Israelis want American leadership.
Now consider again the more complicated issue of Iran: Americans understand that Iran is more problematic than Syria – the "nuclear issue" makes it so. That’s why on the one hand they overwhelmingly support diplomacy and believe that Iran can be "contained for now", yet on the other hand a majority of them still believe that a military attack should be launched if necessary in order "to prevent them from producing a nuclear weapon" (you can see different polls on Iran here).
The US-Israel battle, then, is one that is basically about the framing of the subject at hand: The administration wants to convince Americans that a diplomatic solution is feasible. Israel is trying to build on the deep suspicions of Americans and convince them that they are being duped by Iran. The US administration's advantage: Americans are weary of war and of involvement in the Middle East. Israel's advantage: Iran is the least favorable country in the world in the eyes of Americans.
And what about Israel's chance to prompt American Jews to be more active against the brewing agreement with Iran? The rules of the game are clear: Jewish Americans are generally like all other Americans. On most issues, they are more liberal. When it comes to Israel they can be slightly more hawkish than liberal-non-Jewish-Americans - but still less so than non-Jewish-hawkish-Americans.
Jewish Americans tend to support Israel when such support doesn't put them at odds with the American public- that is, when the public has views similar to those of most Jews, or when the subject is too marginal for the public to care. Moreover, Jewish Americans don't really like to have confrontations with the White House over Israel. They didn't like it when the US had a republican president, and they like it even less when the president is the man a vast majority of them voted for just a year ago.
Israelis can distrust Obama as much as they want (and they don’t trust him). Still, most American Jews generally do trust him, and approve of his foreign, economic, and domestic policies. They also approve of the way he is handling Iran – according to two recent polls by the American Jewish Committee and by Pew. It should be noted that these two polls were taken prior to what we currently know about the likely agreement. But it should also be noted that a significant gap between the way Israeli Jews and American Jews view Obama is hardly a new phenomenon.
Presented with these realities, a high ranking Israeli official asked not long ago: does this mean that for us to have the backing of US Jews we have to first win over all other Americans? It’s even simpler than that, he was answered: Convincing American Jews that Israel got it right and that the administration is wrong is similar to convincing other Americans of such a reality. In other words, American Jews are a valuable and accessible litmus test: by measuring the support Israel gets from them, it can also quite accurately assess what chances it has of getting the support of the rest of America, the public and its politicians.