The Mexican Civil War was launched in opposition to NAJSA.
In 2013, the Canadian PM, US President James Ballantine, and Mexican President Ruiz-Pena met at Mexco City to sign the treaty. Shortly before, an RC-12 spyplane carrying the Guardrail IX device was shot down over Nicaragua. It was sold to Carlos Ontiveros, although the sale was secretly watched by Ghost Recon members including Joe Ramirez and Captain Scott Mitchell.
They are reassigned when Ontiveros launches his coup. The Canadian PM is killed, and Mitchell rescues the other two VIPs. He is assigned to stop the coup, and they liberate M1 Abrams tanks. Eventually Ontiveros and his son are killed.
Just afterward, Juan de la Barrera and his mercenaries continue the rebellion. Mitchell and the Ghosts stop de la Barrera, and Mitchell is seriously wounded when he lasers the missile for the EMP bomb.