The 12 apostles in Jerusalem wrote many epistles to the saints. The 12 disciples in America never wrote anything (at least that we know of). Any explanation would be helpful.
There really wasn’t a reason to send letters with long explanations of doctrine among the Nephites.
First reason: If you recall, after Christ’s visit to the Americas, the Nephite/Lamanite Civilization lived in peace and harmony.
And it came to pass in the thirty and sixth year, the people were all converted unto the Lord, upon all the face of the land, both Nephites and Lamanites, and there were no contentions and disputations among them, and every man did deal justly one with another. 4 Nephi 1:2
Most of Paul’s letters dealt with misunderstandings in doctrines and disputes as to the doctrines that Christ had set forth. They didn’t have the benefit of all knowing Christ beforehand. A few learned from the beginning. And more followers came throughout His ministry. Some knew more than others. Many had problems with catching up.
But among the Nephites, they all heard the word together all at once. They knew the doctrine. And ALL were converted.
Second Reason: Travel. Among the Old World Saints, the apostles were spread over a LARGE geographic area by comparison. Travel was arduous and costly. Not so among the Nephites. It seems that the Nephite civilization only covered a fairly small area.
I’d imagine that both the clarity of doctrine and the smaller area both generated a Church culture where there was tremendous communication and consensus regarding doctrine, policies, and procedures. As a result, there was really nothing to write about that wasn’t already contained in the Book of Mormon.