Probably a bigger factor is that, in the early 1940s, virtually the entire infrastructure of Europe was destroyed. In March 1945, there were no operational bridges across the entire length of the Rhine river. All of that infrastructure was rebuilt in the late 1940s and the 1950s to then-modern high speed standards; by contrast, the US has to make do with infrastructure upgraded at great cost around the 1910s.

Before WWII Great Britain, Germany, and France all had about twice the rail they have now . After the war, cars and trucking made a big difference and system length decreased fairly steadily as a result because lots of track got rebuilt as roads.

Europe also had a big military imperative to build railways pre-WW1: Trains let you move your forces faster, so you can build up a concentration of forces in one location to attack or reinforce a defensive line.

So no state in continental Europe wanted to be on the losing side of a railway gap.

This is probably a much bigger factor than usually thought. Military necessity will trump budget constrictions and property rights. Railways pre WW1, roads during and after WW2 and in preparation for the Cold War.