The US black population is somewhere between 13-14%.... Obama won the presidency because although the bible belt states are monopolized by the white (racist) republican vote, those states are the some of the least populated states, sans Florida, Georgia, & Texas(which is becoming more liberal by the day). Obama had enough liberal votes from heavily populated states like NY, PA & OH that Romney couldn't catch Obama in the electoral.... The re-election race victory for Obama was narrower but still the same result.
That's it.. 13%