Why does the US support Israel?

I can't think of any advantages to the US supporting Israel, but I can think of a whole bunch of disadvantages.

There's no way anyone can look at all the Jews in the American government, the finance industry, and the media/entertainment industry, and NOT honestly conclude WHY the US shows such support for Israel.  The Jews may only be 3% of the American populace, but they wield x10 larger economic influence due to their professional positions.