As a non-practicing Jew, I'm ashamed to say I know what you mean and what you say is correct. I grew up with a strong Zionist feeling...but that sounds very Spielbergish, doesn't it? I don't know why the majority of American Jews appear to be against the political waves that want to help them and Israel.
I've repeated my theory ad nauseam. Lots of people agree with me. With all the great conservative Jewish columnists out there (Mark Steyn, Charles Krauthammer, Zev Chafets, Jonah Goldberg, Bill Kristol, Dennis Prager, etc), I'm baffled why none of them have echoed the same idea. It's seems pretty elementary to me.
To answer your question, Ashkenazi Jews were persecuted by blonde haired, blue eyed, primarily rural, primarily nationalistic, and fairly religious Northern and Eastern European Christians. They came to America, took a look around and saw that there was a huge glut of blonde haired, blue eyed, rural, nationalistic, religious Christians living in the South and the Midwest. So they said "these are the people we have to look out for".
Most of these Jews settled in big cities where they had no contact with rural Americans and were ripe for accepting the "city slicker vs. country folk" prejudices that you find all over the world. Many of these Jews were sympathetic to the Socialist and Communist movement. They simply could not fathom that Americans practiced an enlightened form of Christianity, and that's why America was good to the Jews. Instead they bought into the idea that America was good to the Jews because of "seperation of Church and state" (a myth that appears nowhere in the Constitution) and the likes of the ACLU.
Meanwhile, America's oldest Jewish communities were in the South, where they were NEVER subject to persecution. Many Jews had high positions in the Confederacy (Judah Benjamin is one example). But back in the big cities, Blacks, Italians, Greeks, Asians, Hispanics, etc, griped about the prejudice that they were subjected to, and the Jews bought into this idea that they had to align themselves with these minority groups so they could stand together against the great "White Trash" majority. What's ironic, is that whatever antisemitism that these Jews were subjected to, came at the hands of these very same big city minorities that they felt such an allegiance to. I guess they thought that if Blacks, Italians, etc, were calling them "kike" and "Hebe" behind their backs, imagine what all those rednecks in Alabama would say about them.
Sadly, this mentality still persists today.