Had you been stuck in LAX overnight, then CX may have been on the hook for any accommodation or food costs if indeed they were the ones who changed your HKG-LAX-DFW to a HKG-DFW flight thus making you miss the last flight out of LAX. Thankfully this didn't happen. You can always write into CX to relay your distress and disappointment, but don't expect anything from them as they have not given out comp for worse stories found here on FT.