[T]he situation of the Israel under judgment in Gal 2:15–4:11 corresponds to the existence of the godless Gentile sinners, and the corollary is that believing and justified Gentiles obtain the same position as Jews justified by faith. Therefore, in Christ all alike share the same biblical promises.
As expressed in Romans, the story of Israel concludes in sin, exile, and, ultimately, restoration. Ironically, Israel’s existence under the law is used to illustrate the common experience shared by Jews and Gentiles alike: all are fleshly and under sin.
And in Ephesians,
Gentiles find salvation not by being joined to a living Israel as proselytes, but by being raised with a dead Israel from the grave of their exile, as beneficiaries with them of the grace and mercy of God