Maybe the unenlightened Chinese will prefer Americans as foreign teachers, but those in the know are not so favourably disposed towards them. The reason being that, in my experience teaching in China, Americans in the classroom spend a lot of time comparing things in China to back home and telling them how things are great there. Chinese don't like hearing this at all!

Other English-speaking countries tend to supply teachers with a little more diplomacy and they usually last longer. Besides, the standards of oral English that some Americans produce indicates that they are in urgent need of some remedial ESL training as well - even after making allowances for the deficiencies in American English.

You are right about African Americans though