As always, a very detailed, interesting, and helpful response from Bernhard! Thank you very much! I am an American, which is why I recognized the tune as "My Country 'Tis of Thee," (which I incorrectly referred to as "Let Freedom Ring/Of Thee I Sing") and not "God Save the King." Of course, both of these songs follow the same tune, but since Dickens was English, I guess Debussy was quoting "God Save the King."