That's funny, I'm black too and I used to have white people misread my facial expression a lot. I ended up training myself to use a different, more "neutral-looking" resting face in public.
I'm white and people think I'm angry and unapproachable. It is uncommon in my country of origin to smile for no reason, and if one doesn't do it here in the US, people mistake what I consider my "neutral" face as hostility. I'm still working on it. Worse yet, it's also not common in the Russian culture to maintain constant eye contact with strangers, not doing which in the US means that one is trying to mislead and they're not trustworthy.
