I had a similar situation. Is was an award in J on CX HKG-ORD connecting to ORD-XXX on AA. I was using US miles. CX cancelled the HKG-ORD flight, and moved me to the next day, but the AA flight never changed, so I would have missed the connecting flight by a day.

I called US and they said there was no award space on the ORD-XXX on AA the next day, so I was SOL. I asked them to call AA to request that they open 2 award seats.

I gave the US agent my AA EXP account # and asked the US agent to mention to the AA agent that I was EXP. I guess that helped because they opened the seats for me.