AA in a way has fifth freedom rights for the DFW-ORD 777 as that flight number and aircraft continue to LHR. The official routing of the route is DFW-ORD-LHR, as it is all under one flight number. The reverse(LHR-ORD-DFW) is the same too. However, AA can pick up and drop off pax at ORD though.
As far as I know, pretty much all of AA's 777 domestic flights are repositioning, or routes with 2 legs, which the first or second leg is longhaul.
As I mentioned, DFW-ORD-LHR and LHR-ORD-DFW are perfect examples of this. I know AA flies 777s between DFW and MIA. Those go onto S. America. A weird thing is that DFW operates DFW-MIA-MAD flight#68 (correction?). The MIA-MAD leg is operated by a 763, but the DFW-MIA leg is flown by a 757.
Give me a break, I created this username when I was a kid...