I don't see the problem, since the show was not made for an American audience. As far as I know, blackface is completely unknown in Japanese culture. To them, it's something one group of foreigners did to another group of foreigners more than 50 years ago. They don't know what it is, and there's no reason why they ever should think about it. If a TV show in America showed a pair of chopsticks in a bowl of rice, would that be offensive? Now, if they dressed as Koreans, there might be a problem.

Would the goggles and red cape still be mandatory?