The point of excluding inhabited ice regions is not due to lack of population its due to lack of potential developable land. My point is to put yourself in American shoes when they developed after WW2, there was so much abundance of developable land, resources, and wealth plus this new automobile coming onto the scene, it was natural that it was going to develop the way it did.

What makes you think these states only developed after WW2, and how does this explain the US having the world's best passenger rail system in 1920?

Here's a map of it; see how densely it links up this vast country: https://vizettes.com/kt/rta/maps/usa-rr-1920.gif

Meanwhile, the Netherlands was completely car centric just like the USA until the 1990s, when they decided to start redesigning roads to prioritize walking and cycling. Are you sure these things are really inexorably linked to geography?