Mexico

Mexico (メキシコ), officially the United Mexican States, is a country located in the southern portion of North America. Mexico shares boarders with three countries; the United States of America to the north and Guatemala and Belize to the southeast.

Background
The border between United Sates and Mexico near the shore of the Pacific Ocean was the front line base of the Return of the Winged One which had its main base in Central America. The Sixth Sense Headquarters (第六の感覚本社) is located in, Mexico.

Toaru Majutsu no Index Light Novel Volume SS2
On the Second Friday of October, Misaka 14333 was one of the Sisters sent to Gemstone Mining research organizations around the world. She was sent to Guadalajara, Mexico, at the Sixth Sense Headquarters, to destroy the facilities and rescue the gemstone there. During her periodic progress report, she had just blown up the main entrance to the research building.