It is important to recognize that Book of Mormon lands had boundaries and to identify what those were.
Israel is an example or type of a promised land / area that was given by God that has promises and a stewardship (i.e. consequences, good and bad) tied to it, and distinct borders. Modelers should not treat Book of Mormons boundaries so willy-nilly, the Jews living in Israel sure don’t!
Book of Mormon lands were surrounded by bodies of water called “seas.” The Jaredites Land Northward was entirely surrounded by seas on all four sides and the Nephite Land Southward was surrounded by three seas (we are never told what was south of where Lehi’s family landed, all migrations were north).