I am planning on going on to work for Copa airlines in Panama and skip the regionals in the US since I have dual citizenship, and then come back a few years later to a major. Does anybody know if pilots for COPA can jumpseat on US airlines for free or is this not possible?

Most carriers have reciprocal agreements with other part 121 carriers,
I doubt Copa is on any of them, AA has no foreign carriers on the list.

extremly good luck with COPA, I know why are you going, but no Central American airline or better said, no south of the border airline have that advantage of travelling on jump.

Best