Red state ports handle more tons of cargo than blue state ports!
Remember that the Pacific fleet of the red-state country would be located at Alaska, Guam, and allies’ ports.
The Great Lakes are international waters with access to the Atlantic via the St Lawrence Seaway. Most of the red states are in the Mississippi River watershed, so the only oceanic ports they use are in Louisiana. Charleston is now as deep enough to handle ships with the deepest drafts. Anchorage Alaska is also, and it’s ice-free year around.
Every country in the world engages in international trade. No country in the world is self-sufficient. The blue states wouldn’t dare embargo us because they need our help to get from one blue state to the other. They wouldn’t want to lose the business at the ports.