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The level of detail you are seeing is a combination of the renderer you are using, and the fact that Chile is not a rich Western country. Doing the same for England, would result in a lot more detail, because there are lot of people in England putting personal time into contributing to the map.

The Garmin tools start from the actual map data, not from a rendered image, and filter it in their own way. An example of the detail in a well mapped part of Chile is https://www.openstreetmap.org/relation/167454#map=16/-45.5853/-72.0589&layers=D However, even there, there you are likely to find that most of the things in the map are actually being rendered, whereas, in England you are likely to find lots of features that are not considered worthy of rendering in the standard rendering. As a simple example, select the transport map on the above town, and there is no additional data, but do it England, and you will normally see many bus routes appearing.

Also, there is a specific forum for Garmin mapping, and you are more likely to find people who are expert in the Garmin map preparation tools there, than on this forum, which concentrates more on the collection of the map data and its use in general, rather the the specific case of using it on Garmin devices.