You took the words right out of my mouth.
Until Chinese films became popular here, the only martial arts known were Samurai films (ie: Seven Samurai, Musashi Miyamoto) and then there are the military personnel who came back from Okinawa and Japan with Black Belt and advanced kyu levels in Shotokan, Shorin Ryu, Shorei Ryu and Kyokushinkai as more examples.
It's very easy to find Karate instruction in this country (good and bad), especially if you're in major cities. That being said, it was available and blacks flocked to it.