Canada doesn't have domestic auto companies, yet we manufacture auto parts and assemble automobiles destined for the US. From my understanding, this was negotiated as part of the trade deals. There is no good reason for them to desire cheap Canadian labour, weak Canadian unions, or weak Canadian environmental regulations. For one thing, Canada is known for none of those things. On the other hand, Canada had a lot of things the US wanted: access to the Canadian market and access to Canadian resources. I wouldn't be surprised if something similar happened when trade deals were manufactured with Mexico. While Mexico isn't on the same economic tier as the US, it isn't a third world nation that people like to paint it as.

As for companies looking for loopholes, it may be fun to blame it on Asian manufacturers. I would suggest that Americans take a good long look in the mirror. US companies were outsourcing assembly to Mexico long before Mexico came under the NAFTA umbrella. Quite often, at least with electronics, those US companies were using parts manufactured in Asia. Should Asian companies hold themselves back, should they avoid using the same practices as their American counterparts, just because it isn't fair to Americans? If anything, they have less reason to because Asian countries are responsible to their own citizens, not to Americans.

Your comment sounds like you are arguing with me but you are actually agreeing.

I am not "Blaming Mexico" - I am pointing out that the policy as I described it made no sense from American perspective. You are right that the American manufacturs did assembly in Mexico (form Asian components) before as well but it's the same point - an essential Asian good masquerading and benefiting from being a "north American one"