"There are quite a number of Jews who are Republicans and the number is growing."
I hope you are right. As you say, it seems odd that the Conservatives are usually (except the Bucannan crowd) very pro-Isreal and get only 25% of their vote. Could the pro-America thing be a turnoff to the Jews. I hear of some American Jews saying they have more allegience to Israel than America and they have been here many generations.
Most American Jews are from families that settled in the US in the late 19th and very early twentieth centuries from eastern Europe (before Israel existed as a nation). They are Americans first, but don't see any contradiction between support for the US and support for Israel, since both are fighting a common enemy for the most part and have been allies for years. The pro-America thing is a turnoff to some Jews just as it is a turnoff to many whose politics were formed in the Vietnam antiwar movement. But leftist Jews, like others who swallowed much of the American counterculture back then, are - as a group - NOT particularly inclined to be pro-Israel, especially in its current war effort vs. the Islamofascists. (Of course, there are exceptions to every rule.)
If you measure allegiance to Israel with population movements, American Jewish migration to Israel is much lower statistically than Jewish migration to Israel from many other countries.