Sure, but only broadly speaking.
In fact, in the 1850s the US usually ran large trade deficits, typically $50 million per year.
These were paid for by exports of specie (i.e., gold) which brought the books back into balance.
So, for example, in 1860 total exports of goods and specie came to around $400 million, of which cotton was just under $200 million or 50%.
These paid for imports of $377 million, leaving a trade/specie surplus about $23 million.
Bottom line big picture: hundreds of large cargo ships in dozens of ports from Galveston, Texas through Norfolk, Virginia picking up cotton for direct shipment to Europe.
Yes, sure, some of it was accumulated in smaller coastal packet ships, but they would carry it no further than the closest deep-water port.
Large ocean-going ships carry cotton directly to Europe, not through New York.
After delivering their load, like any good truckers today, they looked for return loads, and they delivered those loads to the ports which would buy them.
And those would be New York, or Philadelphia, New Orleans, Baltimore or Boston, certainly not backwater Charleston, SC.
Point is: all of these commercial relationships were voluntary, people had many choices and selected those which made the most sense to them.
If they chose Southern owned shippers over Northern carriers, that was their business.
Cotton packet ship, Atlantic crossing ship:
