I was clearly referring to the natives of the United States with that remark. I have been to the pyramids in Mexico and climbed them myself.
Are you unfamiliar with the Mississippian mounds? Cahokia was an entire city built upon high, man made mounds, the largest of which was as big as a pyramid. It was fairly close to Saint Louis, and at its height, was slightly larger in population than the contemporary city of London.
The correct geographical descriptor for this wonderful site is not “close to St. Louis,” but rather “in Illinois.”