For my answer I refer you back to last fall's thread where you and I already went through this at length. I have no intention of going through it again.
Nothing at all. But of course shipments from the North to Mexico would have been similarly interrupted, and you are invited to imagine how long it would have been until other western territories would have chosen to throw their lot in as states of the Confederacy, rather than seek union with the USA.
Similarly, shipments from Central America would have had to travel by sea rather than by the IRCA railroads that later came into being as a result of Yankee development, and the banannas and other exports would have likely found waiting markets in the southland rather than in longer voyages to the north in those pre-mechanical refrigeration days. The exchange of southern-produced light industrial goods in exchange would have further developed such trade and stimulated southern industrial capacity, and it's interesting to speculate as to whether the Panama Canal would ever have come into existance at all.
I believe it was Winston Churchill's article on a fictional Confederate victory in the War of Northern Dominance that World War I might thereby have also been averted. Happy thought, and too bad that that didn't work out that way.
-archy-/-