השם created the Old World and the New World separate, and by the grace of השם we shall return them to that glory.
The proposal is simple: all commercial air and sea traffic from the Old World to the New World is forbidden.
The implementation is fairly simple: the President of the United States sets up an ultimatum and threatens to shoot down any ship that crosses the line. Actually shooting down a ship would be an Act of War (though it might not actually cause a war). Threatening to do so is not. We assume at least one airline will abide by the line on its own accord, and the rest will follow. Nautical traffic will be harder to bluff; we expect the plan would explicitly allow for some small-scale smuggling without an implicit threat of death.
There will surely be political pressure at some point. They will send a ship full of martyrs. You shall not shoot them down, but shall declare them to be on the far side of the line. Blockade them from your ports, turn them around, do not let them enter or re-enter your territory.
With Zoom as it is, the only large business pressure will be Professional Sports. In the short term, they can take the aforementioned nautical routes. Perhaps there will be a registered Treaty Port in Bermuda. Intercontinental leagues will be forbidden.