Does Mesoamerica Extend to Northern North America?

No. Mesoamerica is a cultural-historical region extending from central Mexico southward through Guatemala, Belize, Honduras, El Salvador, Nicaragua, and northern Costa Rica.

Its northern boundary lies near the Sinaloa River (west) and the Lerma–Santiago basin / Tropic of Cancer (east)—roughly the modern Mexican states of Sinaloa, Zacatecas, San Luis Potosí, and Tamaulipas.

It does not include the southwestern United States (Arizona, New Mexico, Texas) or northern Mexico's arid zones (Chihuahua, Sonora, Coahuila, Nuevo León, Baja California), which belong to the Aridoamerica cultural area.

Key Mesoamerican civilizations: Olmec, Maya, Teotihuacan, Zapotec, Mixtec, Toltec, Aztec (Mexica).