Has nothing to do with alpa. What you need..
1. Your company must have a jumpseat agreement with the airline in question...odds are good that you do for any US airline.
2. That airline must accept jumpseaters for international flights...some do, some may not.
3. You will not be able to occupy the cockpit jumpseat on the return flight to the US...you will need an available cabin seat. You will most likely not be able to sit in the cockpit outbound either.
For international, I'd just non-rev on your mainline partner...higher priority and better shot at first class. Some AAirlines will never allow jumpseaters in first class...