The shows will provide him with positive, heroic Asian men as role models -- something that is rather lacking in American media.
These positive memories and associations could very easily carry over to an interest in Japanese language and culture when he's older.
Unless you mean specifically japanese here, you are sadly mistaken.
Bruce Lee, Jackie Chan, Joan Chen, Chow Yun-Fat, Jet Li, Shu Qi, Russell Wong,John Cho ,Jang Dong Gun, Pat Morita, George Takei, Yunjin kim, Moon Bloodgood, Zhang Ziyi, Ken Watanabe, Michelle Yeoh, Devon Aoki, Lucy Liu, Sandra Oh, Ming-Na Wen, Masi Oka, Tia Carrere, Kelly HU, Bai LIng, Sendhil Ramamurthy, Daniel Dae Kim Gong Li, James Hong, Lea Salonga, Parminder Nagra, Shin Koyamada.
Are only a few of the Asian actors now prevalent on the Hollywood arena..