NAFTA, like all modern forms of economic cooperation, is a huge mass of bureaucracy. It's not going to be implemented until the later half of the 20th Century after a modern bureaucratic welfare state exists.
These forms of economic cooperation always have a form of political interest involved. Why do these two or more states want to go through the hassle of economic integration?
So what would be the reason for economic integration among all these North American states? The CSA fought a war so that it wouldn't have to cooperate with anyone outside their region. So wanting something like NAFTA could only happen after a very big change happened in CSA politics or foreign affairs.
So we have about 100 years of history to make up before we can even intelligently talk about this. It is just as plausible that North American peacefully integrates economically as it would fight each other in a series of brutal continental wars.
I do see cooperation between the US and a liberal Juarez influenced Mexico to balance out an implicit alliance between the CSA and British Empire (including Canada). Both blocs might have various treaties and such. The US might have a lot more political and economic influence in supporting a liberal Mexico to support a fellow democracy once threatened by European neo-colonialism. So not just the economic ties developed under the Porfiriato, but also encouraging political development and liberalization. Maybe Porfirio is encouraged to not keep running for office, and there is no Mexican Revolution.
But getting the two blocs to cooperate as well? You would need a major crisis to encourage economic cooperation. It's certainly possible, but would probably require something similar to our timeline - military cooperation against a rising and dangerous Eurasian power that lead to a history of continuous cooperation on various issues, and then a world economic crisis and rise of overseas economies that would be an incentive to create a common market on North America. And that requires lots of butterflies.