Daffy uses a huge mallet to clobber Elmer on the head, just as he does to Von Vulture (using VV's own mallet that he had formerly been braining Shultz with) and Hitler.
The all-American bad boy's "Ameri-CAA!!!" holler and imperious use of his heavy weapon against Achmed is reminiscent of Von Vulture's use of the Howitzer cannon to shoot Daffy as a human cannonball out over Germany, accompanied by his grandios shout of "Heil, Hitler!"