Question was asked: “Why do Christians call themselves Gentiles if the New Covenant was designated for Israel only?”
The New Covenant i.e. the Gospel of Jesus Christ was supposed to be the fulfillment of God’s promise to Abraham in Genesis 12:3,
‘And I will bless those who bless you,And the one who curses you I will curse.And in you all the families of the earth will be blessed.”’
Subsequent to destroying all of humanity save eight, God set apart a people group after His own Name who were provided a codification of the moral law combined with civil-ceremonial-dietary edicts instructing them in holiness as God is Holy (Exodus 19:6 – Deuteronomy 14:2). God established Covenant[s] with these people through the Patriarchy of Abraham, Isaac, Jacob, through whom God introduced His Messiah to the World. God’s eschatological Plan and will for the children of Jacob (Israel) was that they would be a blessing to every family of the Earth as these people would proselytize every Nation in the Gospel of Yeshua through the New Covenant established in Yeshua’s blood atonement (Matthew 26:28). The ENTIRE focus of the Torah, the prophets, was preparation for Israel’s role in the Gospel of the New Covenant (Galatians 3:24-26). Yeshua’s ministry was focused on the “lost sheep of Israel” and reunification of man and God by grace through faith (Matthew 15:24).
Unfortunately, Jacob’s children broke God’s covenants; Jacob’s children rejected the Gospel message; Jacob’s children rejected the Messenger, Yeshua, the Messiah of not only Israel but of the whole World (John 3:17; 1 John 2:2); Jacob’s children falsely accused their Messiah of blasphemy; Jacob’s children conspired with Rome to savagely beat and bloody their Messiah and ultimately murder Him upon a tree; Jacob’s children demanded freedom for a convicted murderer while demanding that their Messiah’s blood be upon them and their children (Matthew 27:25).
For this reason, the New Covenant i.e. the Gospel of Yeshua, was taken from Israel’s children and given to the Gentiles (Romans 11:25) and will remain in custody of the Gentiles until their numbers (Gentiles) entering the Kingdom by faith are fulfilled. Meanwhile, Israel has been blinded by the veil of unbelief (2 Corinthians 3:15); Israel’s heart has been hardened (Romans 9-11) and as a result, only a remnant of Israel’s children will escape the “second death” in Perdition and these will primarily be that generation which sees Messiah’s second-advent at the end of the Tribulation dispensation initiating the Millennial Reign of Yeshua (Isaiah 10:22; Romans 9:27).