Literary: Nephi uses an imagery that would have been familiar to the Old World Jews, but not necessarily to those of his community who never knew Jerusalem. The strait path and narrow gate have meaning for Old World peoples who understand ancient walled cities. With a walled city, there was commerce inside the walls, and the main gates would be large with a broad pathway to accommodate many people coming in and out. Jerusalem also had several other small gates. These gates were not for the mass of population, but served as convenient entrances and exits for other purposes. The reason for a narrow gate was one of protection. The purpose of a walled city is protection, and gates are weak points in the protection. The larger the gate, the more area that must be protected. Thus a narrow gate would be available for convenience, but small so that it might more easily be guarded.
With such an understanding of narrow paths and gates, the listeners would understand that this mode of entrance into the kingdom was not for the great masses, and also that there was not much leeway in the passage.
Translation: The use of such Old World-reliant terminology may suggest that this particular wording owes more to the King James Version than Nephi’s actual words. At the end of his life, Nephi would be speaking to more and more people who had never seen such walled and gated cities. Mesoamerican cities may have had some fortifications, but they were not walled cities in the sense of a Jerusalem. They had large causeways for the main entrances, but no gates. Thus this imagery works best on a population that had seen Jerusalem. By this time the Nephites would have had proportionately few of such people.