So, technically, AA doesn't have to do anything for you. If you write in to them explaining the situation, they MAY waive the change fee and let you use the ticket for a different trip. You shouldn't expect them to, but, sometimes, if you speak to the right person, it does happen.

If they don't, I wouldn't cancel the ticket at all. If the flight ends up being significantly delayed or cancelled, you could just get a refund based on that.