8) no worries! although death note is pretty popular (and ah yes it's one of my favorite animes), i do not think america would recognize the characters from death note, but he is probably familiar with the name because he's good friends with japan.

so i wouldn't worry about it! america is more familiar with media from his culture, not from another-- even then, he doesn't fourth wall EVERYTHING..
but things like star wars, star trek, american comic book characters, etcetc-- he would probably recognize.

so no worries 8)