This war comedy came out in March, 1919...four months after WWI had ended. Because of this, I am pretty sure the film was not nearly as successful as it might have been had it come out before the November, 1918 Armistice. By 1919, many folks were sick of the war and I am sure they just wanted to forget it and get on with their lives. Plus, the very broad humor and very obvious propaganda seemed ill-timed coming out long after the benefits of such a movie could have been felt.
Now if this isn't enough, I must say that "Yankee Doodle in Berlin" is not a particularly funny film. The humor is rather broad and at nearly an hour in length, the picture seems to drag. Normally, a Keystone comedy lasted 20 minutes or less (often much less) and so seeing many of the familiar studio stars lost its appeal after a while. About the only strength is to history buffs...especially as a few actually looked like the actual Germans (such as General Von Hindenburg and Admiral Tirpitz). Still, this only makes this a curiosity and not a particularly fun or enjoyable film. My overall score of 3 might just be a bit generous...and I love silent comedies.