It is important to note that this is not a unique thing to Japan. There happen to be several Japanese brands but there are tons of others from outside of Japan.
Art Audio, Sugden, KR, Canor, Audion, First Watt, Triode Labs, Raven, Sophia, First Watt, Wavelength are just a few I am thinking of off hand that produce the same type of amps in the US or Europe.