> Japanese construction is a lot more robust than American housing, and also tends to have extremely good soundproofing on windows and doors.

This must be a different Japan than the one I'm familiar with, where exterior walls are often uninsulated and only a few inches thick and single-pane windows are still the norm in a lot of housing. I wouldn't be surprised if soundproofing were better for railroad-adjacent buildings, but compared to American homes the soundproofing here is surprisingly poor.