This was in color, I think from the nineties; I believe it was a TV episode not a full movie. A man lives in either Cleveland or Cincinnati during World War Two and has some sort of argument with a relative perhaps his uncle. I dimly remember something about a U-Boat. In any case, he travels and when he returns to the home he left there are Nazi songs on the radio and IIRC a Nazi flag on the wall. This was somewhat like Bradbury's "A Sound of Thunder", I believe, in that there was something he did during his journey that led to the Nazis winning the Second World War.
The show is Darkroom (1981-82) and was hosted by James Coburn.
The episode is "Stay Tuned, We'll Be Right Back" (IMDB) from November 27, 1981.
In the second story, "Stay Tuned, We'll Be Right Back", a father discovers that the crystal radio set he bought for his son as a hobby is receiving radio broadcasts from the 1940s.
At first its just radio serials and commercials, but he's soon hearing Morse-code broadcasts from World War II. When he intercepts a communication revealing the position of a troop carrier that his father served on, which was sunk on Oct. 15, 1942, he becomes obsessed with somehow changing history to save his father's life.
He adapts the crystal radio to send as well as receive, and broadcasts a Morse-code message in German to divert the troop carrier. He succeeds in changing history, and therefore the present. His father lives, but with the unintended consequence of the Nazis having won the war.