Exactly why there would be an English subtitled version of a Japanese-spoken movie.
Because people who do not speak japanese may want to watch a japanese movie without having to learn the language.

The Parasite Eve movie is available in the U.S. with English subtitles,
The americans spoke the english language last time i checked
I don't understand what you're saying. Are you insinuating that they should have said "American subtitles" instead of "English subtitles"?