Maybe he just tags it "Sousa" to get hits? To be fair, as a search term, "Sousa" gives you pretty much the same things as "classic American marches"...
And for some reason, I always think this song would be hilarious if sung by puppet chickens a la The Muppets...
From the title, I was expecting to hear Marilyn commenting about her feelings on Barber, which would have been much more entertaining (and surprising)