Considering that the US can pull out of NAFTA anytime our nincompoop of a president wants to, I wouldn't count on NAFTA being around long enough for the UK to join. (Not sure if the story made it overseas, but Trump was just about the pull out of NAFTA, but a 10-minute conversation with his son-in-law changed his mind.)
As for Brexit, it was sold as
- Continental Europe sucks
- Continental Europe needs the UK more than the UK needs Europe, therefore
- UK will get to keep the good parts of the EU without the bad parts.
Now that people are waking up to the fact that the UK won't get to keep the good parts without the bad parts, they have determined that Continental Europe sucks. Sounds about right.