Not only was "made in Japan" established by 1985, but it was already thought to be superior in popular culture:

In Back to the Future Part III, Dr. Emmett "Doc" Brown--the 1955 version of himself--discovers that the DeLorean time machine car has broken down because of a faulty chip made in 1985.

Doc Brown: Unbelievable that this little piece of junk could be such a big problem. No wonder this circuit failed. It says, "Made in Japan."

Marty McFly: What do you mean, Doc? All the best stuff is made in Japan."

That might be a cute joke, but a better indication would be VHS camera used in the first Back to the future movie - 1984 made in Japan JVC GR-C1. The cool innovative tech gizmo wasnt US made.

This probably isn't the most valid use of Google's Ngram viewer, but it looks as if "Made in Japan" started taking off about 1980, "Made in Taiwan" slightly earlier, but on a lower trajectory, and "Made in China" really in 1993.

https://books.google.com/ngrams/graph?content=made+in+China%...

It is interesting though. I wonder why Japan peaked in 1991? Perhaps as simple as the start of the Chinese ascendancy in exports, and from then onwards 'Made in China' just gradually replaced 'Made in Japan' for the pejorative sense of the phrase, which is why it has now returned to pre-1980 levels, which would be a simple factual usage of the phrase?

The Japanese economy went into a big recession in the early 90s. https://en.wikipedia.org/wiki/Lost_Decade_(Japan)

My own memory of 1985 was that "Made in China" was just starting to get off the ground. Example: at the time, Black & Decker had bought out GE's small home appliance division. I had a Black & Decker-branded hair dryer (that had been a GE product beforehand) and was rather surprised to see "Made in China" on it. I felt it to be a bit ominous even at the time, never mind that products imported from Japan, Taiwan, etc. were already commonplace.

According to the data I've seen, the first huge growth in Shenzhen was centered on 1983, with the biggest peak coming around 1991.

I think it was "made in Taiwan" around then. Japan was a rich, developed nation and investment into China proper hadn't really started.

There was another one: "made in Hong Kong".

I remember seeing that in various things, ever since my father pointed it out. It was common enough to exist in daily lingo.

Most of the time it was a synonym for cheap knock-offs.

I also remember seeing "Made in Macau" on the bottom of little toy cars I played with when I was a kid, as well as other cheap toys and things. Bit of a contrast to today where Macau is the Vegas of the east

Macau didn't seem to be a big player relatively:

https://books.google.com/ngrams/graph?content=made+in+China%...

Macau has been the Vegas of the East (or, the Monte Carlo of the East) for a long time - Portugal made gambling legal there in 1850 https://en.wikipedia.org/wiki/Gambling_in_Macau

downsizing was also introduced around then - during the time of James Goldsmith and the corporate raiders