The point Zeihan makes is that world trade as we know it a recent invention. It exists purely as a result of the US commitment to protect trade from piracy around the world. Prior to that, the system was one of isolated empires each protecting their own routes.

As the US is largely self-sufficient in energy and will likely start becoming self-sufficient in a great many things, it needs the rest of the world less and less.

Those shipping lines, which mainly benefit the rest of the world, start to look like an expensive relic with each passing year.

All it takes for an end of shipping is for the US to stop protecting shipping lines which mainly benefit foreign governments.