I thought I heard it all, but Norway having an advantage in public transport potential over the USA because of geology is one of the best ever.
Norway is essentially made of mountains, fjords and ice.
It's incredibly long and thin, has ZERO plains and it's almost impossible to go on a straight line from point a to point b
A good chunk of the country has multiple months with only a few hours of sunlight per year
It's scarcely populated.
The public transportation system in Norway follows roads that were already in existence meaning the path through the mountains has already been forged rendering the existence of plains or mountains largely immaterial to serving most of their population where they currently reside aside from point to point trip durations. It might be a relevant discussion if construction was primarily based on public transportation needs, however E6 would have been completed\upgraded\maintained without the existence of public transportation so that does not apply here.
I also don't know what relevance the amount of daylight has on the operation of transportation along established routes. It certainly doesn't seem to impact it much at all given the functioning transportation services available in places like Alaska or Norway.
As for scarcely populated if you haven't ever been to northern Norway I would suggest looking at a population density map. You'll see most of the people in the north live along a very narrow corridor served by 1-2 major roads. Run a few buses and ferries along those routes and you have now served the majority of the northern Norwegian population.
Now compare that to a population density map of South Dakota and it quickly becomes apparent that to serve the same percentage of population you need far more buses and roads. Keep in mind that your typical bus is going to run you around $500,000 and then costs around $115 per hour to run in terms of driver salary, fuel, maintenance etc. So, depending on how you run your bus, you are looking at around another $250,000 a year for operation. Decentralized bus service adds up fast. Inclement weather service also becomes more problematic the more decentralized your road system is
Serving the majority is rarely a problem when you plan public transport. The people insisting on living on remote islands (Røst, Utsira, Ona), and in the end of fjords where there are so many landslides, avalanches and rockfalls that you have to have a ferry and passenger boat on standby, is what causes grey hairs on the planners' heads. "The percentage" that we need to serve is 100. If you want to live on Røst, we will take you there by public transport
https://en.wikipedia.org/wiki/R%C3%B8st. If you want to live in Geiranger during the winter months, we will provide a "Avalanche ferry", with a printed time table, ready for when the rocks and snow comes crashing down:
http://www.sunnmoringen.no/incoming/article307338.ece Some years we have to use dynamite to get the avalanches to go before the tourists start to arrive. That makes manning the avalanche ferry easier, since we can tell them to be ready this tuesday, instead of some time during the next few weeks.
E6 in your description sounds like a broad highway. The reality is that it is regularly closed do to storms, avalanches and landslides. Almost all of it has paving and two lines now, but not everywhere.
Earlier this year a landslide over E6 caused a lot of problems: the only possible detour was via Finland, and took 7 hours:
https://www.nrk.no/troms/jordraset-i-troms-gir-omkjoring-pa-700-kilometer-1.12353626 In cases like that, we have to use boats, helicopters and planes to ensure that people get where they need to be. Also, all restrictions on snowmobile use were lifted. When E6 crosses the polar circle, it also goes over Saltfjellet (the Salt mountain). Tuesday this week, they had +1*C, heavy snowfall and gale force winds there. I'm not sure how many days each winter the transport over Saltfjellet gets restricted, but it is not few. "Kolonnekjøring over Saltfjellet" is a common part of the weather forecasts, it looks like this:
I don't doubt that planning and operating public transport in the US has it's own challenges. But the biggest challenge in my part of Europe is that we have to provide it for everybody, no matter where they live, no matter what happens. And beacuse of this, geography and weather is a big issue, and the stats that show where the majority live is of little relevance.