ID this Vinyl Sofa from Japan  

Most likely American with...
Most likely American with Japanese sourced legs and/or wood.

I have a set
of teak nesting tables made in Japan. Each and every component of their construction is impression stamped Japan. (under the legs too, just like that)
In the 70's the Japanese made cheap copies of American guitars and drums etc. from the 60's which really killed the market.(Slingerland , Grestch, Gibson etc.) Why wouldn't copy furniture as well? They obviously like the style and are heavily influenced/interested in western culture etc etc.
I just dont see how importing wooden legs from Japan would be cheaper than making them in-house, after producing the rest of the sofa.

"I just dont see how importin...
"I just dont see how importing wooden legs from Japan would be cheaper than making them in-house, after producing the rest of the sofa."
It was actually quite common. I am sure there was some financial advantage to doing it.
Wood legs and Japanese plywood were imported by American manufacturers and used on their furniture. They almost always retain their "Japan" stamps.