Slavery was a key element during the Revolution. The writers of the Declaration of Independence are talking about freedom and equality, how could this not affect those in slavery listening? Many slaves fought during the Revolution in the hopes that the freedom they were fighting for would at the end of the war, extend to themselves.
If you want to watch a good movie, and see a little of this idea in action get Mel Gibson's The Patriot. There is a very interesting African American character fighting in it. It is not a true story but a well written one about attitudes towards African Americans and slaves and their feelings about the Revolution.