I'd be a lot happier if he was calling for the revocation of NAFTA but that would mean a lot of US manufacturers that have outsourced to Mexico would be faced with the quandry of whether or not to move production back to the USA or to accept high cross-border transit fees imposed by Mexico (which is probably what a Mexican exit from NAFTA would entail).

Then there's the sheer volume in trade of Mexico's agriculture and fossil fuel sectors across the border, most of which takes place under some provision of NAFTA or other. I recall hearing claims that crude oil is shipped to Mexico at present (under the 2015 revocation of the 1970s-era ban on crude oil exports from the USA, which may be playing a partial role in current high gas prices). However, I've also hear refined products are shipped back to the USA from Mexico, not sure about that.

Probably just political posturing.