Most people even in the south have not had properly cooked grits! and you are correct, polenta=grits. Polenta is usually yellow corn and grits white. Also cooked a little differently. It was funny when northern people would come to Charleston and snub their noses at grits. Then you ask them if they eat polenta and they say they love it! Get them to try properly cooked grits and then they concur. Great base for all kinds of things.
If you want proper grits, check out a company called Anson Mills. They produce grits from heirloom corn as well as flower and heirloom rice that was produced in SC in the 18th and 19th centuryies