Europeans added sugar to make the modern chocolate. Sugar is an old world entity. The ancient MesoAmericans did not have sugar, which was imported by the Portuguese to the Americas after Columbus.
Perhaps sugar from cane was missing. Agave nectar, Yacón syrup, and Stevia leaves are sweeteners sourced from the Americas.
The Mayans also had vanilla... which is the “bean” pod of an orchid native to the Americas.