First of all, Tokyo Rose was an American. Second of all, the song emerged just after the end of WWII, which a great number of people were emotionally involved with.

The song was/is pretty funny, IMO, as were a great number of songs by Mr. Abe Burrows (who, as I recall, was the lyricist for Guys and Dolls, among others.) He also wrote The Girl with the Three Blue Eyes, Heintz the Huntsman and a bunch of others, predating the revered Tom Lehrer by a few years

Lighten up, folks.