Star Traveler asserts that Judaism and Christianity are both Abrahamic religions and that Islam is not -- but elaborates a theological position, rather than a description. Jews more than just the divinity of the Messiah, they reject most of the fundamental tenets of Christianity -- original sin, for instance. Messianic Jews, who are a growing group and are like the First Church in Jerusalem (of whom we hear from James [Jesus' brother] and Peter) are evidence of the tight integration of Jews and Jesus Christ. You don't find such a thing as "Messianic Muslims" (either in history or the current day).
There is no connection between Islam and Christianity. But Jews and Christians have the same God as Abraham, Isaac and Jacob -- who is the One true God ("Allah" being one of the many false gods that the God of Abraham, Isaac and Jacob stands against).
You will not find a single Jew from across the spectrum of liberal to haredi Jews who would accept a Messianic Jew as truly being Jewish. Liberal Jews may happily eat pork -- but agree that someone who accepts Jesus as Messiah and the Son of G-d and all the rest of it is Jewish? That's meshuganeh!