Not much can be done about that. Only way to really fix it is with a strict regional filter. A dedicated server could also help a little to improve the consistency of the connection as well.
Though what your seeing in the kill cam is what the host Xbox sees, which is never accurate for every player. Essentially the person you went up against had a better connection and ping to the host which gave him an advantage over you. So the only way to beat someone in that situation is to outwit them by flanking,hiding,hectic strafing,jumping,dropshotting, or unless they are just a terrible player who have the reaction time of a sloth and shoot as if they are blind.