1. Because most cultures have a blast objectifying women as opposed to making them strong, and tend to like to jerk off the male ego. Gender roles could also apply here. Just general gender issues.
2. I imagine very possibly so. Though Anime/Manga originated in Japan, I don't see why the art can't exist in other areas, and even so China could easily be the setting of a manga/anime as there's more than man could hope to try and count.
3. Dragon Ball Z proved you can have 5 seconds of punching and kicking and 3 hours of screaming in the same stance powering up and people will eat that fucking shit up.