Hardly half-a-year after Israel's Central Bureau of Statistics said the Promised Land's 5.3 million Jews now constitute the world's largest Jewish community, ahead of America's 5.2 million, a newly released study conducted by Dr. Ira Sheskin of the University of Miami and Dr. Arnold Dashefsky of the University of Connecticut suggests there actually are 6.4 million American Jews. Longing for lost Israelites has been a Jewish obsession since the Ten Tribes vanished, and the rumored discovery of lost brethren, let alone 1.2 million of them, has turned on Jewish imaginations at least since the ninth century, when a black traveler named Eldad Hadani claimed he had visited the lost tribes of Israel. Hadani, who "reported," for instance, that four tribes - Naphtali, Gad, Asher and Dan - were living in East Africa under one king with Samson's and Delilah's heroic descendants in their midst, and that all of them alternately studied and fought in three-month intervals - was obviously a charlatan. Sheskin and Dashefsky are not charlatans, and the first to concede this is their leading adversary, Hebrew University demographer Sergio DellaPergola. Yet the "discovery" of so many new American Jews is already making some there respond with the kind of tragically clueless awe that Hadani inspired among medieval Jews. First, in the narrow statistical sense the expanded number is clearly questionable, with all due respect to the surveyors' insight that American Jews are relatively affluent and as such prone to be unavailable when the surveyors call. Considering that the survey is based on data drawn inconsistently from disparate localities, based on calls often conducted decades ago and overseen by local organizations, any survey of American Jewry is dubious. Moreover, any previously uncounted Jew is clearly a badly assimilated Jew who could not be found listed officially in any Jewish framework. Sadly, no revision of American Jewry's size will cure it of its illnesses. There is no arguing that every day more American Jews die than are born, that more American Jews marry non-Jews than Jews, and that American Jewry's numerous organizations, synagogues, community centers and social institutions attract barely one in three American Jews. Now, if the new survey is right, then it means that institutionalized American Jewry has been losing even more Jews than previously assumed. BACK IN the spring, when the Central Bureau of Statistics officially said Israel's had become the world's largest Jewish community, we noted that this is a revolution in Jewish existence, considering that the Promised Land had not enjoyed such a status since the times of Jeremiah nearly 2,500 years ago. Now, even if Israel's emergence as home to the world's largest Jewish community has yet to arrive, it is still fast approaching. Nowhere else, certainly not the US, are intra-Jewish marriages as abundant, young, fertile and durable as they are in Israel. Indeed, Israeli Jewry is in the process of eclipsing American Jewry less because of its own resilience and more because of its brethren's tribal degeneration. Never before has a Jewish community squandered an opportunity for Jewish blossoming as American Jewry has. Had its leaders invested in nurturing the local Jewish future only a fraction of the resources they allocated for defending Jews elsewhere, the US could have now been home not to 5.2 or 6.4 but to 10 million Jews. If even passively bred, this is a homegrown Holocaust. It follows that both American Jewry and the Jewish state must not let the Sheskin-Dashefsky study confuse them with its numbers: the question is not how many Jews there are in America, but what to do about their rapid evaporation, and the answer is that American Jewry's task is not to count bodies, but to nourish souls. THE SPIRITUAL crisis of American Jewry is all the more troubling considering the physical threat currently faced by the Jewish state. What if, God forbid, the Bomb that is being prepared for us actually arrives here: Who will then restore the Jewish future? I don't know who, if anyone, will be up to such a task, but I can assure you of one thing: it won't be American Jewry's virtual members, whether they number one, two or three million; certainly not the way American Jewry has been led for the past 100 years. American Jewry has had some accomplishments in recent generations, most notably its role in releasing the Jews of the East Bloc and in standing up for Israel in moments of crisis like '67 and '73. Yet American Jewry has also had some harsh failures, like its leaders' frequent resistance to East European immigration in its first years, and the cold shoulder many of them gave to the Zionist cause in its first decades. Far more tragic was American Jewry's failure to unite and fight in the face of the Holocaust. No less significant, if less dramatic, was mainstream American Jewry's embrace of the Sunday school illusion, where Jewish identity and heritage evaporated while real education was handed over to the public school. NOW HISTORY is imposing on American Jewry, whatever its size, the formidable task of being "the other camp," the one that Jacob set aside as he and the other half of his family approached Esau as they returned to Canaan not knowing what his hostility would make him do. I always wondered what it was like to be in that frontline contingency, the one assigned with bracing for the worst while the other camp watched from afar. They may or may not have wondered how the family would survive should they be slain. Then again, the ones placed in the front camp were Jacob's two mistresses and their children, in other words the ancestors of the Lost Tribes, while the ones in the rear were the ancestors of today's Jews. Maybe the ones in the frontline knew they could depend on the rear camp for their tribal continuity. Can we Israelis, from our current frontline position, make this assumption about our lost brethren in America?