1 Nephi 13:12 wrote:And I looked and beheld a man among the Gentiles, who was separated from the seed of my brethren by the many waters; and I beheld the Spirit of God, that it came down and wrought upon the man; and he went forth upon the many waters, even unto the seed of my brethren, who were in the promised land.
I'm of the understanding that Christopher Columbus was more or less glorified in Joseph Smith's day and generally said to have discovered America. I hardly think Smith knew anything of the four voyages led by Columbus; it's reasonable to think he and others of that time and place assumed Columbus discovered America, even the very continental shelf of the east coast not far distant from Smith's hometown. I assume that Joseph Smith thought that Columbus discovered America proper! At best, his schooling and education regarding Columbus would have been crude and misinformed. It's even possible that Smith read the popular poem The Columbiad that was written in 1787 and made readily available to the public in his era and vicinity.
Now, with that said, it's easy to equate how visionary Nephi said the "seed of my brethren" in the future "promised land" would one day be visited by a man (Columbus) who being wrought upon by the Spirit to sail across the ocean blue in 1492 to discover the American Indians. I believe that is exactly what 23 year old Joseph Smith had in mind when he dictated his Nephi prophecy to Oliver Cowdery. I don't think for a second Smith knew that Columbus only discovered the West Indies and never set foot on the so-called "promised land" which was the very land the Revolutionary War was fought and the American Constitution drafted upon the promised land being the same land the Lamanites & Nephites lived out their days according to that which is written in the Book of Mormon.
Every time the "land of promise" is mentioned in the Book of Mormon it is rooted within the concept that it is America proper, the very soil in which George Washington and the framers of the Constitution established liberty through free government on the choice spot of ground reserved for that very purpose. In fact, the way the Book of Mormon reads you might as well remove Mexico, Central America, and South America from the map because they aren't included. It's all about the Constitution and America proper. It's all about Joseph Smith's homeland and the Hill Cumorah!
If you don't believe me, then for God's sake, at least believe Joseph Smith! That is exactly what he implied and envisioned. I can feel that to be so. Amen.