Well if there was ever a film with a visual language that was laser-cut to its objective, it's
Momotaro: Sacred Sailors (aka Momotaro's Divine Sea Warriors, which is how I remember it in the days before its restoration and Western release). The history of film is intertwined with its use for propaganda, with some of it's most effective techniques such as montage being the product of a cinematic arms race to use it to persuade an audience to a viewpoint rather than merely entertain. The Second World War was perhaps the Golden Age of Propaganda, with all sides using film to their own ends. Animation was a particularly popular medium for propaganda, with Disney producing dozens and dozens of hours of propaganda films, perhaps most famously the Donald Duck-starring
Der Fuehrer's Face which won the Oscar for Best Animated Short.
Japan's animation industry was certainly not what it is today, and certainly had nothing to compare to Mickey Mouse or Donald Duck or Bugs Bunny. What Japan did have was its folklore, and it used the image of Momotaro, a boy who was born from a peach and fought alongside animals against demons. In 1936, several years before Japan would attack Pearl Harbor, Momotaro fought a demon who was unmistakably modelled on Mickey Mouse - undoubtedly Japan defending itself against an attacking, demonic United States.
Following the success of Momotaro's Sea Eagles in 1943, director Mitsuyo Seo was allowed to make a sequel - this time slightly longer, which gives it the distinction of being the first feature length animated film made in Japan. In Momotaro: Sacred Sailors, the primary is not America but rather the British. The animation is undoubtedly influenced by Disney and Ub Iwerks, but is probably more similar to the work they were doing in the mid-late 20s than contemporaneously during the war.
Fantasia, arguably Disney's crowning achievement, was screened in Japan during wartime. Mitsuyo Seo definitely saw it, as did Yasujiro Ozu who famously said "Watching Fantasia made me suspect that we were going to lose the war. These guys look like trouble, I thought." If you compare Fantasia, with it's visual and aural spectacle, made to entertain but also a stunning artistic achievement, to Momotaro: Sacred Sailors, with its black-and-white rink-a-dink animation, it's obvious how wide the gap is. Fantasia is the product of a country with money to burn and minds fresh and inventive - if either/both of these were distracted enough from putting Mussorgsky to Chernabog to concentrate on defeating Japan, what chance would Japan have? We all know the outcome.
However, Momotaro has the entire Japanese animation industry as its legacy and I don't think anyone would seriously argue that it hasn't closed the artistic gap with its American equivalent in the interceding years.