Truthfully it is impossible if for no other reason than that you can't easily say what counts as "imperialist propaganda" or an "American movie or TV show" to begin with.

Like if Cats 101 puts stock Vaguely Middle Eastern flute music for 15 seconds in its Egyptian mau segment, does that count as imperialist propaganda? It exoticizes Ancient Egypt, playing into orientalist tropes that form part of the ideology of imperialism. Or does it not count as imperialist propaganda, because you're still learning about a country in the Global South, which could inspire further curiosity? Or do these things cancel each other out? Or does it depend on the viewer's personal interpretation as guided by their personality and circumstances? Does the depiction of domesticated carnivores and cat shows promote classism and speciesism and lay the seeds of white supremacy blood quantum shit, more cornerstones of the ideology of imperialism?

How about The Mythbusters? Does that count as imperialist propaganda because they don't do land acknowledgements for the Alameda Bomb Range? They made use of Miwok land without the permission of the Miwok people and present this as normal and fine. Hell, because that bomb range is located right next to a jail and the crew had to cooperate with the sheriff's office to use it, does that mean it's copaganda too? Another component of imperialist ideology? Or is there some revolutionary use for a TV show that gets young minds interested in ballistics and science in general? Or do these things cancel each other out, or does it depend on the individual viewer's interpretation as guided by their personality and circumstances?

There is imperialist propaganda everywhere for those with eyes to see. At the same time, you can never fully account for the dialectical relationship between the text and the audience.