The FBI file on Benjamin Freedman, who was a convert from Judaism to Catholicism, is an interesting read.

Messianic Christianity is essentially a form of Evangelical Protestantism. Protestants are Judaizers; for example, they use the Masoretic text produced by Jewish Rabbis during the middle ages as the basis for their Old Testament as opposed to the older Greek Septuagint used in the early Church and which is still used in Orthodox Christianity.

Per Freedman Jesus wasn't Jew, but a Judean. Iesus Basileus ton Ioudaion, is usually translated 'Jesus King of the Jews' but it would be more accurate to translate as 'Jesus King of the Judeans.' This very important distinction has been deliberately suppressed by Protestant Judaizers who were very successful in popularizing the slogan 'Jesus was a Jew.'

The religion were think of today as Judaism didn't exist during the Second Temple Period. The Biblical Hebrews were essentially pagan, their religious practices as different from rabbinical Judaism as from Christianity. By the second temple period, three major religious factions has emerged in Judea: the Sadducees, the Essenes, and the Pharisees.

The Pharisaical movement supplanted the old Aaronic priesthood of the Sadducees shortly before the time of Christ. The religion we think of today as Judaism evolved from that of the Pharisees; the people Christ warned his disciples about, and who were responsible for his crucifixion. The main holy text of Rabbinical Judaism, the Babylonian Talmud was completed approx. 500 AD. For their own benefit, Talmudic Jews have tried to pass themselves off as Hebrews, Israelities, etc., as forerunners of Christianity; but their claims of direct descent from ancient Israelites are dubious and their religion evolved contemporarily and in competition with early Christianity. Until recently, most Christians understood the Nation of Israel, God's Chosen People, to be synonymous with the Church. Again, you can thank Judaizing Protestants for the confusion.