What Hermann means is that New York has always been an "exception" in that a large portion of its white population has been ethnically AND religiously Jewish (Jews are an ethnicity as well as a faith. There are Jewish atheists, agnostics, and even Christians!). As a result, the "culture" of "white" New Yorkers has been different from the rest of the country, as has the politics.
Where I disagree with him is that the type of Christians and Europeans who settled in the northeast (Italian, Irish, Portuguese, Greek, etc.) had an even greater impact on the cultural/poltical outlook of those states than the Jewish population did, simply due to the larger numbers of the aforementioned groups. I still laugh when I met an older gentleman from western Pennsylvania who thought that New York was "majority Jewish."
Did he call it "Jew York"? That is the nickname you hear from people like him down here, in Pittsburgh, and in South Jersey. They are under the delusion that the whole city is Jewish except for Harlem and the South Bronx, where the blacks live, Chinatown, and parts of Brooklyn, where the Italians and Irish live, and even most of the suburbs beyond obvious exceptions like Newark. Trying to explain the reality of the situation to the simpleminded is difficult.