He sounded so interesting, I Googled him and found a Washington Post Book World article, too. There Mitchell cited some of his other influences, including other "experimental fiction" and the idea that "...there is nothing inevitable about civilization." A cool idea.
Although he doesn't use standard spec fic settings, Mitchell still adopts the spec fic precept that reality is not a boundary that a story must respect. He also lives in Japan, which must be an interesting experience for a Westerner. Being visually and culturally different from everyone around you must be good practice for writing about people, disaffected and otherwise. Being the alien gives you a different perspective.
Let's face it; writers are neat people.