[MMM]

One of the best Japanese teachers I had was an American guy, because he understood the difficulties of learning Japanese in a foreign language.

I don't think it matters if you are black as opposed to white if you are teach (I assume) Japanese to non-Japanese speakers. However, just as some Japanese prefer to learn Japanese from native speakers, the same is true of some foreigners learning Japanese.

I applied to one school in the US as a Japanese teacher, and was told flat out they wouldn't hire a non-native speaker to teach. I then questioned the legality of that stance, and was then told to send my resume. You don't need to ask if I got the job...I could imagine you might get that reaction from some schools in Japan, where the legalities of hiring practices are different than the US.