Black Actresses is a category we use for female Actors from Europe and North America whose parents initially came from Sub-Sahara Africa (drop the code, we mean from black-skinned Africa which means stars who are originally from North Africa do not qualify).
We have Nigerian Actors, South African, and Celebrities from Africa categories. In Africa, color is not the issue, ethnicity and nationality are. So we keep Africans out of this category. A black actress from the United States is just that, a black actress in our category. If she is from the UK, the rest of Europe or Canada, then she would have two categories, Canadian Actresses, or European Stars, or British Actresses to add their primary category.