To state that the war torn status of Japan and Europe was the sole reason for their modern rail lacks credibility. Further, Japan has extensive mountainous terrain. It isnt flat like the eastern seaboard (where the NE Corridor is just baaaaaaaad). Any extended rail trip in Japan will have you running along side mountain cliffs, at the edge of the ocean, _through_ mountains, across highly active seismic terrain, past locations prone to flooding and mudslides, you name it. Yet some how, even during the Great Tohoku Earthquake, _the rail never stopped running_. Moreover, Japan simply executed eminent domain anywhere they needed land, and did not muck about with NIMBYs. Fundamentally, the Japanese culture is about cooperation looking out for communal interests. There are a lot of negatives that come with such a heavy focus on the community over the individual, but mobilizing for the common good is definitely not one of those negatives.
Here is a good read on why their bullet trains never stopped, despite the enormous scale of the Great Tohoku Earthquake:
