Are there any non-Japanese manga/anime authors or studios? Manga and anime famously originate from Japan, and the vast majority of the big names in manga and anime are Japanese; Hayao Miyazaki, Hideaki Anno, Hiromu Arakawa, and Masashi Kishimoto come to mind.

Outside of Japan, I can really only think of one creator who had their work become an anime/manga: The Deltora Quest series was adapted into an anime and manga and was created by an Australian writer, Emily Rodda.

Aside from Rodda, however, are there any* international creators, particularly from the Western world, that have successfully published manga (or anime) in Japan, manhua in China, or manhwa in Korea? Have any Western studios created and produced** anime (or rather, anime-influenced) series?

* - An exhaustive list is not necessary; a few examples from various countries and maybe some stats versus Japan, if possible.
** - Not as a result of outsourcing.
Don't know of a non-Japanese studio that produces only anime, but the series Oban Star Racers was produced by a French studio, "Sav! The World Productions" along-side Bandai and Disney.

The Studio 4C production "First Squad" has writing credits to Russian studio Molot Entertainment Film.

As far as mangaka, there's a lot of Korean manwha artists/writers that get published in Japanese serials. I don't think that necessarily makes them "mangaka". The series "Blade of the Phantom Master" by Youn In-wan was serialized in "Monthly Sunday Gene-X" in Japan (published by Shogakukan). Shin Yong-Gwan also had his first couple of works published in "Young Champ". 

As far as the western world Frederic Boilet is probably the most well known, born in France but draws comics in Japan.