I am not an expert on foreign trade.
However, last July I had to ship a set of used Dunstall silencers to a friend in Canada.
I took them to UPS here in New York and asked them to give me an estimate of shipping charges.
I was told that shipping would cost over $100.00. I was shocked.
The UPS guy told me that cross border shipping incurred a customs charge, and then he handed me 3 long customs forms to fill out.
I reminded him that the silencers were used, not new, and he told me it didn’t matter.
I don't know if NAFTA applies to all trade across the border.