The Toltecs.
Toltecs
Because Mexico is not the same as the US state of New Mexico. It is an independent country with a developing economy and has Mexico City as its capital.
Too broad a question. Some answers would be: developing economy, emerging market, southern neighbor of the United States, bicentennial country.
Mexico is the southern neighbor of the U.S.
It is on southern New Mexico (the US state), but it is located on northern Mexico (the country).
Mexico is the country that borders the southern United States.
Mexico City is the capitol of Mexico, which borders the USA
The U.S. southern border is formed by Mexico and the Gulf of Mexico.
The closest southern neighbor would be Mexico.
Both are equally right; however, Southern Mexico is a specific region encompassing three states: Oaxaca, Guerrero and Chiapas; southern Mexico is a more general area that could be anywhere south of Mexico City, down to the border with Guatemala and Belize.
it is
Northern Mexico has a lot more mountains and southern Mexico has a lot more rivers.