Most of the NAFTA traffic will be thru Texas.
While much of the traffic will originate through the boprder states, I assure you that it will soon spread all over the US as Mexican truckers drive to the nearest load that will get them back to the border.
The laws against this will not matter, much as they didn't during the era when the Teamsters constituted most of the drivers, and the ICC was the "authority" that "regulated" the trucking industry. So-called "Gypsy's" ran unregulated loads all over the country in direct contravention of the Federal rules, because they could do it much cheaper and faster than the regulated companies.
This situation will be no different than that was except that the flow of money will head south of the border and the US will become dependent on Mexican truckers. When the day comes that they strike, the US economy will collapse in short order.
If you don't believe me, then go find a retired trucker who remembers the teamsters strike of the 60's. They very quickly got the concession they were looking for, because the stores, and in particular the grocery store rapidly emptied and the people started telling the govt to settle the strike no matter what is took. My entire family was inmvolved in the trucking business in those days, and I remember it very well.