SPG posts transfer to AA on a weekly basis. Request done before 10am Tuesday got processed the same week and will show up in your AA account the following week. I forgot whether it is Mon or Tue.
I gather you know that CX opens up its F award seats 7 to 10 days before departure. HKG-SFO tends to have the biggest last minute availability.
Keep in mind AS program is not as flexible as AA program. For example, AS charges $100 for ANY change. AA does not charge anything as long as your origin and destination remain the same - so you can change date, you can change routing if better routing becomes available after you ticketed. AA charges close-in booking fee of $75 for non-elites. Dont know how much AS charges.
The free change on AA can be advantageous - say, you initially find availability HKG-YVR on CX, you can book a HKG-YVR-DFW-SFO itinerary AA award. Later CX opens up HKG-SF0, you can change your itinerary to HKG-SFO for free if it is an AA award. You would have to pay $100 per ticket change fee if it is an AS award. You could even fly HKG-JFK-SFO using AA award and still pay the same 55/67.5K (one-way) and you have the option to change it to HKG-SFO.
I would transfer to AA instead of AS because of the uncertainty of CX availability.