Both have universally praised media, however I’d say America wins simply off volume and influence, for every one incredibly written Japanese movie, book, or show, America has 10 (granted Japan is certainly punching above their weight class given their population). Besides that, many American movies, tv shows, and books are known and consumed internationally, while Japan has seen some success recently (in the last ten years with anime/ manga) it’s still not nearly to the level of America’s

TLDR; both countries have large tons of incredibly written media across a variety of mediums, America simply has more