>That means a small number of people employed making the cars benefit But those small number of people who benefit plus the whole of people in their supply cha

>That means a small number of people employed making the cars benefit But those small number of people who benefit plus the whole of people in their supply chain, people that also drive demand for whatever the other people paying more for cars are offering. The point I'm trying to make is that international trade doesn't give any multiplying magic. Simply separate the states in your country and whatever trade between them will become "international". It would be the same trade as before with the only difference that now you don't get to tax whoever is benefiting the most, one gets to play tricks with the currency, etc. etc.