Yes I agree Israel was a nation but they weren’t the peculiar people and Holy nation that God chose.
God will fulfill his promise to King David, which is the gospel of the kingdom, in 2 Samuel 7
8 Now therefore so shalt thou say unto my servant David, Thus saith the Lord of hosts, I took thee from the sheepcote, from following the sheep, to be ruler over my people, over Israel:
9 And I was with thee whithersoever thou wentest, and have cut off all thine enemies out of thy sight, and have made thee a great name, like unto the name of the great men that are in the earth.
10 Moreover I will appoint a place for my people Israel, and will plant them, that they may dwell in a place of their own, and move no more; neither shall the children of wickedness afflict them any more, as beforetime,
11 And as since the time that I commanded judges to be over my people Israel, and have caused thee to rest from all thine enemies. Also the Lord telleth thee that he will make thee an house.
12 And when thy days be fulfilled, and thou shalt sleep with thy fathers, I will set up thy seed after thee, which shall proceed out of thy bowels, and I will establish his kingdom.
13 He shall build an house for my name, and I will stablish the throne of his kingdom for ever.