A mid-'90s Turner Entertainment VHS, now out of print but available used online, entitled Bugs and Daffy: The Wartime Cartoons features a number of cartoons satirizing Hitler and Nazi Germany, with a few thrown in that make brief references to the war years.
The “Private Snafu” cartoons, which were made for the Army by the Warners studios, are public domain due to the fact they were made by the government. These appear on a number of DVDs, including Image Entertainment’s The Complete Uncensored Private Snafu.
Although you only mentioned the Warner Bros. studio, any reference to wartime animation cannot be complete without a reference to the prestigious Walt Disney studio. During the war, Disney produced over 400 educational films for use by the U.S. government and military, as well as propaganda films featuring the familiar Disney characters poking fun at army life and Nazi Germany, and also encouraging Americans to buy war bonds and pay their taxes to support the war effort. A number of the propaganda shorts, excerpts from the training films, and the feature film Victory Through Air Power are available on a now out-of-print (but available used) DVD called Walt Disney on the Front Lines.