@my_happy_place
I have volunteered on a couple different J-dramas now whose pre-subs themselves came with all the “Americanisms” including those you mentioned above as swell as the general tone you spoke of. The slang and colloquialisms were everywhere! I’ve even seen it in pre-subs for historical C-dramas! I can’t speak to the specific drama you’ve described and whether it came from a volunteer or pre-subs, but in my experience, it seems like a (disheartening) trend in pre-subs.
I believe @irmar said the video is here at RViki. I could be wrong.
On YT I have been a witness of many people that tried to emulate American way of speaking, and so called writing the American way by using gonna/wanna etc…
At first, I thought they were ‘‘ghetto talkers’’ trying to write subtitles on YT, but with a good research work; I found the Instagram of the people doing this atrocious subtitles, and most of them haven’t stepped foot in American soil.
They just learned how to fake sounding like a young American boy/girl as they write as if they are American. Most of them are in their late 20’s but love to imitate the young American kids. There’s even an Arab girl that has perfected this way of ‘‘talking’’ that she has millions of viewers (myself included). It’s amazing how good she is. I also found someone from Spain that loves to use a lot gonna/wanna etc., but I think that one was blocked because I can’t find his page anymore since I reported him a while ago. Unless of course, he has me blocked, and I can’t tell if that’s why I don’t see his page. Not that I care much either.