I am not shooting it down, I am 100% in favor of such a system and scrapping the current system. Was just pointing out something I saw as a potential problem. I would love it except if the next democrat elected to office then uses it as carte blanche to turn us into a wholesale socialist entity. I might then have problems with the repercussions, but I'll gladly deal with that fire when we come to it.
And your thoughts about NAFTA are pretty right on, too, unfortunately. Neither party wants to enforce the border, for whatever reason. Any tax plan will play into it- short of a revolt, or militia action, there's not much anyone can do about the illegal invasion.