If for no other reason, Mexico would want to get taxes on a product that is legally allowed in their country but being sent to another country. The two cannot be completely disconnected from each other. Fox is not proposing any policy change at the moment, nor is he going to openly oppose US 'orthodoxy'. But Jonathan's comparison to Gorby is a good one. Gorby certainly didn't start off with the intention of destroying and dismantling of the Soviet Empire.
History changes the man as much as the man can change history.
And this 'War' is not sustainable in the long term.