Sorry, but this is not a valid point. You deliberately declined the UA SIN-LAX option which would have gotten you into DFW with a delay of 3-4 hours. Instead you insisted on getting rebooked via HKG and LAX which meant that your arrival into DFW was significantly later.

I agree with the previous poster that the rebooking of HKG-DFW to the following day is likely to have been made by AA systems if the initial reserved flights SIN-HKG-DFW were still in the system somehow.

Move on and let it go. I actually think that CX did very well (besides for the delay of the SIN-HKG flight obviously) by rebooking you OAL when CX was not obliged to do this and then accepting to change it to a longer and more complex routing because you feared loosing out on miles/points and getting a middle seats!