Having been addicted to science fiction since around age 10, and with racism such a major issue today, here's a couple of bad futures we need to avoid:
In Philip K Dick's masterpiece 'The Man in the High Castle' - a parallel-world story set in 1962 where Germany and Japan won WWII - what did the Germans do before they flew to Mars and Venus? They exterminated all the inhabitants of Africa.
In David Wingrove's series of novels about a future Chinese-dominated world 'Chung Kuo' there are no black people on Earth...the only surviving Africans are a handful of colonists on Mars.
How easy it would be for our own America to fall into those patterns...