I doubt that many Jaguars would survive in the lawless north of Mexico now anyway.
I think this is like many species - once in a while, they are seen outside of their "normal" range. For instance, there have been penguins found in the N. Pacific. Does this mean that the northern hemesphere is their "normal" range and we should attempt to introduce them there? NO, of course not!
In recent decades, the Jaguars that have been sighted in the US are as likely to be escapees or released from private owners as they are to be truly wild. We, here in the US, have a problem with stupid people releasing exotic pets as they get too big to handle, and I have no doubt that at least a few animals have escaped from the many "rescue" shelters scattered around the SW US.
Big cats would be better served if we bred and released tigers back into their native range - after all, the country with the greatest tiger population on earth is the good old USA.