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If you're studying A level, then don't you need to discuss the style quite a bit? I just googled A level and read a little, but I don't know much about it. When comparing American and British styles, American style isn't just Hollywood, there are American independent films too. That may be something to consider.
Generally when watching them, I find I can rely much more on the quality of British films. Too many American films are made solely for the purpose of money, with $100,000,000+ budgets, and revenues sometimes in the billions. With that much money involved there is also corruption. For example the major companies make it hard for small companies to succeed by manipulating the rating system. If you're with the corporations they tell you what you need to change to get a rating that allows your film to air on TV giving you more awareness and a larger revenue. If you're not with the corporation they won't tell you what to change and sensor your movie. I watched a documentary on it, and it can be very difficult for independents in America.
Also a lot of American films are filmed here in Canada. I'm not sure if film location is something you consider in A level.
And then there's the content. Many American films are about wild and crazy things, like an organization that hunts down ghosts and traps them in a box. They have the budgets to do elaborate special effects. British films tend to be on more realistic subject matter.
I don't know if any of that helps.