Clearly, you have your answer. It's a Wonderful Life is very much the American Christmas Carol. Now you should ask a different question: What qualities do the two stories have in common?
Great stories have great themes. A theme is a controlling idea that everything in the story supports; it is the author's main message to you. Every story worth telling has at least one. (An obvious example is the first Spider-Man movie. Its theme is "With great power comes great responsibility." Everything that happens to Peter Parker supports this theme, and everything bad that happens to him--his uncle gets shot, his aunt goes broke--happens because he forgets this lesson.)
What is the theme of A Christmas Carol? Actually, the great thing about this story is that it has a whole bunch of good possible themes: Christmas is one time of year when you really need to lighten up. Money is no good if everybody hates you. Death makes things a lot more important. There is still time to change your ways. Don't choose money over love. Maybe a dozen more really good themes work with this particular story.
It's a Wonderful Life also has many great themes. The obvious one is that one good man makes a huge difference, maybe a bigger one than he knows. But it has lots of other themes as well. It even has a few of the same themes as A Christmas Carol.
Instead of giving a long plot summary of one of the movies, pick a couple of themes that both have in common and give examples of story elements that support them. One has a bunch of ghosts, the other has an angel. Magical elements! Lots of movies don't have that, but both of these do. Why?
And while both movies are set in the era when they were written or made, both are lasting classics, in part, because they occur when their respective countries are at the peak of their power and influence. Victorian England was when the British had their greatest influence on the rest of the world. America in 1946 was in a pretty comparable position.
Ebenezer Scrooge and George Baily are both in the finance industry. When you think of Christmas, you think of toy stores and Christmas trees and sleigh rides in the snow, but both of these stories are about guys who are trying to balance the credit and debit columns in their ledgers. Is the true spirit of Christmas to be found in a bank office? It's kind of a weird place for a Christmas epiphany. Maybe there's something there!
I think that if you focus more on theme, less on plot points, and give both stories equal weight, you'll find this paper to be a lot easier to write well.