But please explain how all these races melded together, when most people never even left their village in Middle Ages... I'll wait.

Well, let me explain it. The crusaders went to Jerusalem and fucked some Arabs, and then settled there, then Arabs attacked the crusaders and fucked their women. And there was a lot of killing, rapi ng and pillagin (a.k.a melting civilizations) in the Iberian Penisula. And then we got a big fucking wave of "firendly" mongols who just wanted to exchange bodly fluids with European women. But aside form that, no there were not many black people in Bohemia, and if they were they would be treated as a "fancy thing to show of with" by the aristocracy.