The Lord promised that the seed of Nephi and his brothers would not be utterly destroyed. This promise has been fulfilled. The Lord named all of the various groups of people who are part of the living remnant of the Lamanites: “the Nephites, and the Jacobites, and the Josephites, and the Zoramites, … the Lamanites, and the Lemuelites, and the Ishmaelites’ (D&C 3:16–17). All of Lehi’s sons are named except Sam whose “seed (was) numbered with (Nephi’s) seed” (2 Nephi 4:11). Their promised blessings will be discussed later. However, there was to be a great judgment that did come upon them. The angel explained this as being “merciful to the Gentiles” (v. 33). The Gentiles were promised not to be left “in that awful state of blindness, … because of the plain and most precious parts of the gospel” being taken away (v. 32). Mormon further explained how this mercy would be brought to pass.
19 And behold, the Lord hath reserved their blessings, which they might have received in the land, for the Gentiles who shall possess the land.
20 But behold, it shall come to pass that they shall be driven and scattered by the Gentiles; and after they have been driven and scattered by the Gentiles, behold, then will the Lord remember the covenant which he made unto Abraham and unto all the house of Israel.
21 And also the Lord will remember the prayers of the righteous, which have been put up unto him for them. [Mormon 5:19–21]
The Gentiles in the Americas have and will be offered all the blessings that were offered to the people of Lehi. Namely the blessings promised in the covenant made to Abraham. The great judgment upon the Lamanites was their being driven and scattered by the Gentiles.