I hate to say this but could just be North American approach to South/Latin America?
I wish I was joking, but having flown ORD-LHR-ORD and ORD-DEL-ORD several times on AA, I can say with confidence that on the average the service was much better to/from LHR. Mind you, still nothing to send waves of anxiety through CX and SQ management, but one didn't encounter the snappy and rude behavior extended to pax from India.
To be fair, I should note the possibility that the pax from India or South/Latin America themselves may be more difficult and thus invite a reaction? Still, while that could explain FA's attitude, it does not explain AA stocking lower quality food and beverages. That obviously implies something more institutionalized.
However, the issue is just a little more complex: OP's treatment and whatever I saw on India service was much better than domestic pax receive.
So, international/domestic divide trumps other divides.