I think you overestimate the extent to which the war ravaged the countryside. Some cities were destroyed. Most (most!) of the rest of Europe, the towns and villages, wasn't.

It's the cities (and their suburbs) where acquiring new ROW is expensive.

For the most part, the cities in France that could fairly be said to have been 'flattened' during WWII were in Normandy. Paris was scarcely touched. Yet they have a high-speed rail network covering the whole country. Spain was untouched by WWII, yet they have a high-speed rail network. The U.S. somehow managed to build an interstate highway system through every major city in the decades after WWII without being bombed flat. The WWII argument seems weak.

> The U.S. somehow managed to build an interstate highway system through every major city in the decades after WWII without being bombed flat.

The U.S. has essentially stopped building urban interstates since the late 70's, when opposition from residents became too strong to ignore. I don't foresee this changing in the near future.

My understanding is that construction costs in Europe are rising as well due to (among other things) increased use of tunnels in urban area due to opposition from residents.

I'd say that the Western cities were barely touched. When compared to the destruction along the Eastern Front.

LGV operation started in 1981, long after any WWII reconstruction would've wrapped up with several decades of interim land development.