"If the attraction for many of the people of Jewish faith is that their lineage can be traced back to Israeli ancestors then they ought to hold the same devotion to Egyptians, Syrians, Iraqis, etc. that fed into that genealogical pool."

Well, it might to do with fact the the Jews were slaves in Egypt. Apparently they were freed, then they wandered around for some time, then settled somewhere around the land where the state of Israel is today. Here they established a nation and built some big temple. This nation continued for centuries. And for instance, though the roman empire controlled this region, the Romans allowed regions to govern themselves. So, say during the time of Christ, Christ was a Jew living in a region locally controlled by Jews. I.e. Romans that happen to be living in Israel, followed Roman law, whereas non-romans living in area followed Jewish law.