Here's what you do before giving them a call:
Go online on aa.com, and search for brand new flights that you are happy with, as long as they have the same starting (YYZ) and stopping (HKG) airports on your original dates. You actually might be able to find routes with just one stop instead of two (DFW/ORD).
Once you have new flights figured out, give AA a call and ask to be put on those since they changed your flights. If they refuse, then ask for overnight hotel.