Bilateral security cooperation between the United States and Mexico continues to define relations in late 2026, with the Mexican Senate recently approving limited U.S. troop participation in joint training exercises through September 30. Mexican President Claudia Sheinbaum has repeatedly affirmed respect for sovereignty and rejected unilateral combat operations, while U.S. officials have shifted emphasis to intelligence sharing, counternarcotics coordination, and trade negotiations under the USMCA framework. No congressional authorization for offensive military action exists, and recent rhetoric around cartel designations has not translated into invasion planning. This environment of structured partnership and diplomatic channels underpins trader consensus against an invasion by year-end. Late developments such as a sudden breakdown in border enforcement or major unilateral policy shift could still influence assessments before December 31.