You can rent a container going ANYWHERE in the world from the USA for over 1/2 the price of the cheapest one coming in.
Know why?? Because those ships that carry all our stuff in to us, many time go back out 1/2 full.
As much as we like to think of ourselves as the all powerful country that needs noone - we would be hurting just as much as everyone else (if not more) if all countries stopped exporting anything out of their own country.
We are not even close to the world leader in everything.