Highway (road_level 2) textures on the strat map appear to be bugged in two ways.
1) If you skip road_level 1 then the highway textures won't show up in the region until any building is completed in any region. It doesn't matter what building is completed or in which region, but the highway textures will never show up until that happens. Reloading the map and the whole game doesn't change this - you have to build something. Again, this only happens when you skip road_level 1 going directly from no road or road_level 0 to level 2. This also affects the bridge. I tried reproducing this for road_level 1 (that is, skipping road_level 0) but it isn't bugged in this way.
2) Adding highways to the map in descr_strat only works for the first faction (index 0) in the campaign. England is the first faction in the vanilla campaign, so if you add a bunch of road_level 2 buildings around the map you will see that only england's regions have the correct textures and bridges.
I tested these findings in multiple mods including geomod. I'm hoping someone else can confirm or even offer a solution or workaround.