Sociologists say that Americans identify with the Israelis. Most of our ancestors migrated from places where they were discriminated against or actually persecuted. They see America as sort of the new "Promised Land."
The USA has always tried compulsively to be what Europe is not. That started out with not having a king and it just kept going. Look at how many of us today are screaming about not instituting "European-style socialism."
And if there's one thing that characterized Europe for the last millennium and a half, it's antisemitism. While there was a certain level of antisemitism in America, going back to colonial times, it's nothing compared to most of the rest of the world. Even with our "gentlemen's agreements" keeping Jews out of high-class neighborhoods, Jews were treated more fairly here than in any other place they went since Roman times, except China. (In China they were treated so well that they completely assimilated and disappeared, and many Jewish leaders in America are worried that the same thing will happen here. "Be careful what you wish for, you just might get it."
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The Holocaust made our people feel even more strongly. Unfortunately they didn't believe the reports at the time and didn't allow shiploads of Jewish refugees to land here. (The poor
Haitians took in as many as their island could hold and shared their scarce resources just the way Jesus would have wanted them to. These are the people Pat Robertson said deserved their earthquake because God was angry at them!)
Once we saw the photos of Auschwitz (I was born during WWII but I didn't understand any of that stuff until many years later), we made it our duty to help the surviving Jews get a fresh start. Our military ended up being in charge of their refugee camps and there simply wasn't any place in Europe that we could release them to. Antisemitism was still strong there, and many Europeans refused to believe that the Holocaust happened so they felt no guilt or shame. (We tried sending a bunch back to their original homes in Poland and the Polish people started killing them!) So we went along with the British offer to give them some worthless piece of land in Asia Minor called "Palestine" because apparently nobody was living there, at least nobody important, and for some reason we didn't understand (no American studies history because if we ever learned our own we'd be ashamed of ourselves) the Jews were happy to take it.
Too much of what is going on in Israel/Palestine is our own fault. Couple that with the fact that we've always felt great sympathy for the Jews (especially in the abstract, if they're not trying to buy the house next door), and you've got a combination of guilt and sympathy that will outweigh any facts or numbers.
One of the largest blocs of Americans who are not sympathetic to Israel are
young American Jews! More Israelis are leaving their country and coming here, than Jewish Americans are "going home to the Promised Land."