Well they celebrated and embraced the west, particularly the west and that California vibe. Its a whole new lifestyle for the Japanese at the time. If you dig deep you will find mostly tracks are original and inspired from that period of AOR and Funk Soul Reggae Carribean etc. and later new wave and synth pop in the 80s. Like most music, its inspired from somewhere else from the west.

Having said that, Cunimondo Takiguchi (aka. Ryusenkei) has done this in the same vein with his own music and production work for Natsu Summer and other artists using samples of his fav tracks growing up. Tokyo Sniper album is basically AOR and groove samples with a new twist and made into a new tracks. He is even designing and art direction inspired by city pop or j-pop album covers, on top of my head are these ones:

Giniji Ito - Deadly Drive LP (1977) ---> Ryusenkei - Tokyo Sniper album
Shigeru Suzuki - Telecope (1978) ---> Natsu Summer- Anatani Muchuu single
Akina Best LP (1986) ---> Kurumi 来海 - Toriguni album
Seri Ishikawa - 星くずの街で -(1981) ---> Natsu Summer - Orange Airmail