newsokur 内の tamano_ によるリンク 水曜日はアニメの日!!皆で雑談しましょう!(Welcome to Anime Wednesday megathread!! Come and join us!!)
[–]MushroomMountain123 1ポイント 12日前
Most people in Japan watch anime in it's original Japanese. Very few will go as far as watching a Japanese anime's English dub. I have never heard of anyone doing that to learn English. It would be simpler to watch American movies/tv shows with Japanese subs.
Your second question depends on just how widespread you think English in Japan is, which you haven't made clear, so I can't answer that. Movies and some TV shows are fairly popular, cartoons not so much.