https://www.usvisa-mexico.com/mex/index.jsp
Third Country National Citizens
Third Country Nationals (TCNs) already in possession of a visa and who
are currently present in the United States, or Third Country Nationals who
are residing in Mexico (with an FM2 or FM3 status), may schedule an
appointment to renew their current nonimmigrant visas (and/or that of their
children) in Mexico using this system.
