Aside from a brief mention in Daisy Kenyon, I think The Clay Pigeon has the first acknowledgment of Japanese-Americans and the 442nd after WWII. I've been trying to watch this Richard Fleischer B movie for some time, and I'm finally glad to see it.
I feel like the contrasting portrayals of the Japanese (ie. Richard Loo and a deceased Nisei) might be screenwriter Carl Foreman's doing. The historical source for this outlandish little noir is no less fascinating. Otherwise, the story itself is relatively standard fare for the era.