Culture is downstream from race. This is why all European peoples, be they in US, Australia, or elsewhere have similar cultures. Africans everywhere also have cultures more similar to each other than to Europeans.
Although people may mimic or adopt cultures of another race, they cannot create or improve those cultures. Culture is created amongst a homogeneous population. Some people are capable of producing high culture and civilization from it.
Culture is lost when it is mixed into other cultures. If you take all the colorful crayons in a box and melt them together, you get an ugly grey.