It is a choice of citizenship, not a choice by blood. From the time of the Temple was destroyed, all the records were done. Then, who are the Israelites?
The salvation has been given free since the beginning of the world. It was given to the true believers of Christ, no matter the race or nationality.
Therefore remember that you, once Gentiles in the flesh—who are called Uncircumcision by what is called the Circumcision made in the flesh by hands— that at that time you were without Christ, being aliens from the commonwealth of Israel and strangers from the covenants of promise, having no hope and without God in the world.