Yes, It's a Wonderful Life is an example of a "Multilayered Work", as described at the Stanford Public Domain Troublespots. This is one reason films are particularly difficult to determine PD status, unlike images or books which usually have a single layer. See also this guide from the US Copyright Office to see how tricky it can be to determine copyright. It advises that "In many cases, it is important to consult with a copyright attorney before reaching any conclusions regarding the copyright status of a work."   C