Bollocks
"As it is known today, polenta derives from earlier forms of grain mush (known as puls or pulmentum in Latin) that were commonly eaten since Roman times. Before the introduction of corn (maize) from America in the
16th century, polenta was made from starchy ingredients like farro, chestnut flour, millet, spelt, and chickpeas.In Yemen, polenta is primarily prepared from either sorghum meal or barley-meal with an addition of animal fat and made into a thick paste, and is known locally as ʿaṣīd. It is often served in a bowl where soup broth is added as a viand, and eaten with one's fingers. "
Wiki
In short its a pretty generic term of a starchy sort of porridge. In (south) Africa its called 'mealie meal' and is now almost exclusively maize, but used to be millet.
Like most Americans, you think the world begins and ends in the USA