If you ever have anyone doubt this term was actually used, here you go. It's on the cover of a 1993 magazine written by Animation industry types:

https://archive.org/details/wkc-1
I found it in this thread, which is completely unrelated to the topic of this thread but is worth a look before reading that archive. org link.

Back to "Japanimation".
First time I ever remember it coming up as problematic was pre1999 online. I was in early high school so 97/98.

Twilight of the Cockroaches, Ghost in the Shell, maybe Ninja Scroll. One of them had said it in the promo's. I rented one over a weekend and liked it. So I went online and asked what kind of Japanimation to look for and someone responded shortly with "Ja*-animation? how F*cking rcist are you?"

I partially censored that but I hadn't put that hyphen there in my question, I had never even considered pronouncing it that way but ok, yeah; when said that way it sounds pretty bad. Terrible even. It was my first introduction to the idea that there could be other words as bad as that one word, (and that I'd been hearing old people say it for years but that's a different story).

It started a whole *thing* in that forum on a site that is long lost to time; thegia. com(is dead, don't go there Jim)

There was a back and forth about spelling, intent, etc. but the general consensus was many of us had never thought about pronouncing it that way - however once we'd been introduced to the idea no one could unhear it.

Eventually that thread came to a consensus that Anime was better since that's what it's called in Japan. I'd like to think that thread and the others like it helped killed the term since that place had people in the production side of some places at the time. It was the first time I'd seen an actual fight on the internet, people did not want to be told that a term they thought was charming and endearing was racist as hell and the why.

I say all this because the most likely explanation of what ended Japanimation:

So what happened is that a slang term which could be considered derogatory used got used in Toonami ad's and it got enough complaints that the entire industry pivoted hard and fast, which was already underway behind the scenes.

In my ignorance I liked the term, I think its a charming portmanteau that was unfortunately constructed in an innocence I no longer share. The more I understand about why it's kind of racist even if you don't say it with the hard stop on the P... That's also a different story, but the short version is they don't call their country Japan.

I wanted to end there but It's ok to call it Japan. It's ok to call them Japanese; never ever the 3 letter abbreviation. Just lookup where the word Japan itself came from and realize they're mostly ok with the arrangement of how it's used by foreigners in the modern times it might change your perspective on a few things.