The Book of Mormon describes complex governmental systems which were very different to what Joseph Smith would have encountered with Indian tribes in his day.
Bruce E. Dale and Brian Dale comment:
Both the Book of Mormon and The Maya clearly show societies that have large, complex state institutions. For example, the Nephites had (1) some form of elections, (2) armies supported by the state, (3) chief judges and lower judges, and (4) kings (at least part of the time). The Lamanites appear to have had kings at all times. Dr. Coe (p. 63) notes that state institutions were developed among the Maya by the Late Preclassic, consistent with Book of Mormon timing for the references provided.
Analysis of correspondence: Both the British and American civil governments had large, complex state institutions, but the Native American societies certainly did not. This comparison is specific, has quite a bit of detail, and probably would have been unusual to Joseph Smith.– Bruce E. Dale and Brian Dale – Joseph Smith: The World’s Greatest Guesser (A Bayesian Statistical Analysis of Positive and Negative Correspondences between the Book of Mormon and The Maya)
Why would Joseph Smith think that the ancestors of the American Indians were much more advanced than their descendants? How did he know there were systems of judges in Mesoamerica?