Taking into consideration that Japan is little more than a third of a million square kilometers in land area, while the US is over 9 million square kilometers,

Taking into consideration that Japan is little more than a third of a million square kilometers in land area, while the US is over 9 million square kilometers, and the vertical that would impose to railway systems to develop infrastructure similarly. Comparing transit systems from/to the US and most other countries seems to be apples and oranges.