Indeed. You really have to look at settlement patterns and not just a single scalar density. What makes public transport difficult in the US is that suburbs are

Indeed. You really have to look at settlement patterns and not just a single scalar density. What makes public transport difficult in the US is that suburbs are dense enough that a lot of people live there but not dense enough to put in efficient public transport. If you drew a histogram of the Russian population sorted by density, you would find that a very large % of the population lived in dense local areas and a relatively small population is spread over the vast rural parts of the country. Not even just tundra, even Russia West of the Urals is very sparsely populated for the most part.