I wasn't suggesting that shipping goods from Europe to the South was more efficient routing through the Northeast because they could there be placed on railroads or wagons. Stopping in NYC allowed imports to be sorted there and placed (based on orders from jobbers/retailers) on more efficient intracontinental ships headed to various Southern ports. Meanwhile, the intercontinental ships could resupply at NYC or Boston and take an export load back to Europe.
The average cotton farmer in the south was in debt to his "factor" for money to buy land and slaves. The factor in turn represented the farmer to the cotton brokers who in turn represented northern and european investment houses.
One of the underlying premises of the "tariffs were the reason the south seceded" folk (other than to ease their guilt about slavery) is that the Confederates were the true capitalists, not the protectionist North.
Too, after completion of the Erie Canal, one needn't rely only on coastwise traffic. There was the option of transport west to the Allegheny River, and down the Ohio. Water almost all the way -- fast and cheap.