[Discussion] Do you have a western style world?

The world that i am working on is an something similar to a Western Era. There is a main set of train tracks that have been there since before recorded history made from an unknown metal. They have had some luck recreating their own tracks with varying degrees of success. The existing track must be excavated before it can be used. It also circles the entire planet (not straight though, real train tracks have curves) including going over oceans, caverns, and under mountains. They still haven't found the original train that used to travel the rails. Although it is a western, most of the land is ruled by the eternal king. The main reason that he still maintain a presence on the thrown occasionally (once a decade or so) is to keep power hungry people from passing endless laws that just complicate peoples lives.

Now I have some Natives (possibly of the native american variety, but they dont have to be) and they tend to live side by side peacefully (another reason the king still holds the thrown). Although their land is one of the Four Kingdoms(not sure if it would be called that) and as such must provide a Queen to help in the ruling of the kingdom. Since there are 4 kingdoms, there are 4 Queens ruling with the Eternal King.

Anyways, about the Natives, how do have one group remain at a certain technology level if others advance. There is trade between the various groups.