Paxmec is a country mentioned in the book The Legend of Yaotl. Three-thousand years prior to the events of TMNT, the isthmus of Central America was actually a nation made up of states known as Paxmec.
A South American warrior named Yaotl and his army swept across Paxmec, conquering all that lie before them. The most advanced of these states, Xalica, was the final target of Yaotl's conquest. He and his generals, however, were stopped by the Xalican shaman Siba-Noor, who cursed them to stop them in their tracks.