NAFTA only applies to cars (and other goods) manufactured in USA, Canada or Mexico. Everything else gets to go though custom rules and fees as ROW goods.
What that means is that you can buy my LGT and just have it cleared through customs without paying any custom fees as the car was made in IN, USA. I can buy your LGT wagon and have it go through similar process here but again there will be no custom fees.
But if I decide to import EDM or JDM made car from Canada, Mexico or anywhere else the car will be subject to all US custom rules and regulations. Meaning that most likely that car will never see US shores.