Here’s the thing, you could say the same for many small or population dense countries, this is because Japan is population dense but most of the population still live in very concentrated areas, Osaka, Tokyo etc.

One begs to ask the question, Why do Americans need to live so sprawled out? I think the difference is not just one of geography, it’s cultural. It makes sense for Japanese to live in close quarters and there are benefits and negatives for doing so.

Look at France, Germany, Belgium, UK Etc they’re allrelatively population dense countrirs with far more hopeless train networks.

But isn't a railroad much cheaper to build and maintain, than a highway of the same capacity?

No, because rail has fixed routes but everywhere in the road network is connected to everything else.

Yep, rail road is hard to scale down, so it's very expensive to connect every single home to rail road.

Also, rail roads are not walkable, so they cannot be shared with pedestrians, so this limitation forces create two separate roads: one for pedestrians, bicycles, cars, etc., and second one for rail transport. Trams can be mixed with regular road traffic, but trams cannot use regular rail roads because of different construction of rail road.

Also, rail roads are prone to Single Point of Failure problems. To prevent SPF, multiple redundant routes must be built, with lot of expensive junctions between them.

Also, you must schedule your travel.

So, we need something which 1) can be shared with regular road traffic like trams, 2) can deliver loads of cargo efficiently like rail or metro, 3) can be connected to every house like regular road, 4) can be navigated by any car at any time of day or night, 5) be cheaper than regular road for road, cart, maintenance, recycling, 6) can provide power to carts, 7) can provide navigation and scheduling service to carts, 8) be with low delay (fast).

Regular road is 1,3,4,±8. Uber is 1,3,4,5,7,8. Aero-taxi is 1,3,4,±5,7,8. Trams is 1,2,6,7. Metro is 2,6,7. Rail is 2,5,6,7.

Edit: Tram-train is 1,2,5,6,7.

> but trams cannot use regular rail roads because of different construction of rail road.

Actually, they can. https://en.wikipedia.org/wiki/Tram-train

Everything on the rail network is also connected to everything else.

Hardly, especially not in the US where the track is not owned by a neutral party.