It's about making a point, bring awareness, create a forum for discussion, spreading information.

No, it's theater it's like Russia trying to claim back Alaska, they probably have a better legal ground and a much bigger agency trying to (re)enforce that request via other means.

No, it is dredging up an old cow in order to push back against the idiocy of Trump.

Sinking to the level of your opponent isn't going to improve matters. I sympathize with the Mexicans in the current situation, there is a lot to be worried about. But any kind of solution or argument should face a practicality test first and this one will simply waste a whole bunch of time.

It would be akin to the Dutch and the Germans going back a few hundred years in order to redraw our borders (or better yet, the Poles, the (Bela)-Russians and the Germans).