I've noticed that all the rural supercharger congestion problems are on main routes emanating from Southern California. In particular, the bottlenecks lately have been (in order of congestion) Quartzsite, US395 (Mojave, Lone Pine, Inyokern), Beaver and Kingman. This makes sense since such a high percentage of Teslas (especially Model 3s) have been sold in California. Some of these routes (especially Quartzsite) connect Southern California with other high Tesla density cities.
Of course there are also congestion issues in urban areas, but this is less of an issue since there are often so many more options within a reasonable radius. And honestly much of this congestion is caused by locals wanting to charge in prime time, so I don't have a lot of sympathy. The problem with the congested rural superchargers is they are very difficult to avoid, especially if you have a smaller battery or if the conditions are not favorable.
What Tesla has done on major travel corridors connecting high Tesla density cities is create high stall count supercharger sites as a stop gap at strategic intervals. Along I-5 these are Kettleman City, Mount Shasta, Springfield, Centralia and Arlington. You can easily travel I-5 all the way from Mexico to Canada without much concern of a supercharger wait because these large sites exist. The other similar site is Baker on the LA-Vegas route.
So now the web of Tesla density is spreading further away from the coast and Tesla needs to put in large superchargers along the congested routes mentioned above. What I would recommend is 20-stall sites (or possibly 10-stall v3) in Blythe, Cedar City, Kingman and Ridgecrest. The current locations at Needles, Kingman and Inyokern leave something to be desired so might as well just build new ones at the other exit in Kingman and somewhere in Ridgecrest. I know Ridgecrest is not a GREAT town either, but it's got to be better than Inyokern and unfortunately Mojave and Lone Pine don't properly split the distance between LA and Mammoth Lakes.
