It would be culturally interesting, but I doubt it would make a great economic or political difference. As yopu write, kaolinite is found in many places. The key to porcelain production being an economic success is skill and cachet. That is why Sevres, Jingdezhen and Wedgwood are still in business. Getting the skilled labour to the South and then creating a market for the product beyond their region would be a challenge, but might be doable. Maybe a group of European porcelain workers emigretes (the Wedgwood workshops supposedly were home to a fair number of radicals who might feel disaffected, or just be blacklisted/gaoled in the backlash after 1789). They set up a production and it supplies copies of European porcelain during the continental blockade, creating a market as 'nearly the same thing, and cheaper' than Sevres. I wonder if the planter aristocracy will not end up looking down their noses at it because of that.
But even so, most porcelain is produced regionally, not traded globally. The market for upscale ware is small and dominated by traditional makers. Everything else is usually manufactured quite locally (there is no industrial country without at least one porcelain manufacture). The Southern US is a bad location because outbound freight competes with cotton for space (driving up transport costs) while inbound is cheap (due to empty space to be filled with bulky cotton). Porcelain could not displace cotton or tobacco because neither of those are easily produced in the North, Canada, or Europe, whereas porcelain can.