Certainly art generally and movies specifically can have an impact on public perceptions about current events, but this is even one step removed from the Tinkerbell Theory of Iraq. If only good conservatives spend their time and money making awesome conservative movies, then people will clap louder, and THEN the pony will arrive.
While war propaganda during WWII probably helped contribute to the cause, it's because a lot of the war propaganda actually encouraged people to make various sacrifices which probably were necessary, or at least very helpful, to a continued war effort. Clapping louder wasn't especially important. Enlisting was a help.