Historical: We should not be surprised that the Lamanites have taken formal possession of these lands, as they are lands that were abandoned by the Limhites, or the Amulonites.
What is interesting is the statement that the king appoints kings. How is it that we have multiple kings?
In ancient Mesoamerica, as elsewhere, the major political entity was the city. Similar to the ancient Greek city-states, each Mesoamerican city was a government unto itself.
Nevertheless, there appears in the Book of Mormon a conception of ties between the various kings of the city-states. In the later Maya city states this situation would be comparable to the intermarriage with other rulers, or of the appointment of rulers in conquered lands. Each separate city-state would retain its sovereignty, but there could be a loose loyalty to a common benefactor from a larger and more powerful city.
An important historical case of "beholding" relationships between city-states is the relationship between Tikal and Uaxactun:
This is precisely the type of interrelationship being described for the Lamanite kings. Each city would have its own king, but there would be a relationship with another city, and perhaps an overall "king" who dominated one or more "beholding" cities.