Final answer:
Commanders, including the President as commander-in-chief, are responsible for coordinating with U.S. ambassadors in their AOR across military operations.
Step-by-step explanation:
The individuals responsible for coordinating with U.S. ambassadors in their Area of Responsibility (AOR) across the range of military operations are primarily commanders. These include the heads of military branches and, notably, the President in the role of commander-in-chief, overseeing the nation's armed forces. Commanders ensure that military operations are in line with foreign policy as directed by the President. Additionally, the national security advisor and various members of the National Security Council play significant roles in coordination. Intelligence officers may gather data pertinent to such coordination but do not oversee such operations themselves.