Again, your interpretation doesn't line up with all the other scriptures that deal with the matter.
The "children of the promise" in Romans 9:7-8 are those whom God sovereignly regenerates and calls to faith, regardless of whether they are Jew or Gentile. True spiritual Israel is defined by faith in Christ and sovereign election, not by ethnic pedigree.
2 Corinthians 3:6 does not teach that the promise of a New Covenant was made for a physical or ethnic "house of Israel and house of Judah". Instead, it reveals that God has only one overarching Covenant of Grace throughout history, administered in different ways (or sub-covenants) through Noah, Abraham, Moses, David, and finally Christ.
Scripture teaches that God is the Creator and Sovereign Lord of every nation, tongue, and person on earth (Psalm 24:1; Acts 17:26). When God called Abraham in Genesis 12:3, the explicit purpose of the covenant was universal: "all the peoples on earth will be blessed through you."
Paul contrasts the old covenant (the external Mosaic code carved on stone, which brings condemnation and death) with the new covenant (the internal work of the Holy Spirit writing God's law on human hearts, which brings life).
This contrast is not between a Jewish covenant and a non-Jewish covenant, but between the provisional, typical administration of the old order and its permanent, spiritual fulfillment in Jesus Christ.
Jeremiah 31 shows you that God/Jesus will make a new covenant with the House of Israel and the House of Judah after He returns and pours out His Holy Spirit on them like Zechariah 13:1, Ezekiel 36:25, and other Old Testament scriptures show.
Jeremiah 31:27-34
27 Behold, the days come, saith the Lord, that I will sow the house of Israel and the house of Judah with the seed of man, and with the seed of beast.
28 And it shall come to pass, that like as I have watched over them, to pluck up, and to break down, and to throw down, and to destroy, and to afflict; so will I watch over them, to build, and to plant, saith the Lord.
29 In those days they shall say no more, The fathers have eaten a sour grape, and the children's teeth are set on edge.
30 But every one shall die for his own iniquity: every man that eateth the sour grape, his teeth shall be set on edge.
31 Behold, the days come, saith the Lord, that I will make a new covenant with the house of Israel, and with the house of Judah:
32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the Lord:
33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the Lord, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the Lord: for they shall all know me, from the least of them unto the greatest of them, saith the Lord: for I will forgive their iniquity, and I will remember their sin no more.
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