The prologue of the show is supposed to be set in the late 21st century, so they can get away with getting rid of segregation in the pre-war period without delving into the issue all that much. Supposedly, the reason why pre-war America is still locked in the 50's aesthetic despite being set in the future is because they hadn't made significant advancements in developing the microchip in that timeline, and so instead of advancing to the digital era, most tech remained based on big and bulky analogue computing.