The other big anti-Israel faction is comprised of various "ethnic" communities, many of whom support the Palestistineans out of vestigal Third Worldism (most Latin Americans being supportive of the non-aligned movement), the one-sided nature of the ethnic/international press, or merely old school anti-semitism. The most obvious examples are Arab Americans (Muslim or Christian), but you even have cases like the Greek Americans in my area who seem to have an odd belief that the Palestineans are their "brothers", which is residual to the old allegiance against the Turks as well as a common myth that a huge number of Palestineans are fellow Orthodox Christians. If anyone can tell me of an "ethnic" community in the United States that is generally pro-Israel, I would like to know.
You then have another faction comprised of old line WASPs and PaleoCatholics who are merely resentful of Jewish influence and reflexively support the Palestinians as victims of the "Jewish cabal." This is probably the smallest group amongst the anti-Israel contingent, but they often show up on both Right and Left wing forums.