The Book of Mormon maintains a distinction between the remnant of the house of Jacob and the Jews, even though they are both descendants of the house of Israel, which became Jacob’s new name (Gen. 32:28). The house of Jacob is the New World branch, and the word “Jews” is reserved for the Old World branch. The use of that particular word is actually anachronistic for the Book of Mormon as a document that left the Old World around 600 B.C. Originally meaning only someone from Judah, the term “Jew” doesn’t become recontextualized until after the return of the exiled Israelites from Babylon. This places the development of that use for the term after Lehi and his family left the Old World.
Since our Book of Mormon is a translation, the choice of the word “Jew” was probably Joseph Smith’s and represented his best understanding of a term that would distinguish between the Old and New World branches of the house of Israel.