When God divorced the Northern Ten Tribes, The House of Israel, they were sent into the Assyrian captivity. The captivity also included most of The House of Judah, except those at Jerusalem and a few surrounding towns. Scripture calls them “put away and punished”, Matthew 15:24. All hope was not lost and they did not disappear into history.
They were given a promise to one day be called Children of the Living God or Christians, Hosea 1. In the divorce they lost the right to be called Israel (Ruling with El (God)). So, with one exception, from then on they are only called Nations in scripture. The translators not understanding this changed Nations to read Gentiles. This shows the importance for one to faithfully translate a word as found in the Hebrew and Greek texts. Scripture explains in several verses that those Nations were descendants of Jacob.
The New covenant was made only with those of the House of Israel and the House of Judah, Jeremiah 31 and Hebrews 8. That promise has been kept. For almost the last 2000 years they have been for the most part Christians. They have formed many Nations and spread Christianity to the world as scripture prophesied for the physical children of Jacob/Israel.
Romans 2:14-15a “For when the Nations [Gentiles], which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another;)”.
Matthew 15:24 “But he answered and said, I am not sent but unto the put away and punished [lost] sheep of the house of Israel.”