They could transmit on Guard telling the aircraft approaching RWY XX to wave off/go around. The USAF is not known to be shy about transmitting on guard.
Sure they could, and for all we know maybe they did. We don't know the facts yet. Equally there may have been no traffic activity at the base and therefore no reason for the controller to be looking out of his tower cab just in case an airliner, piloted by a qualified crew and equipped with multiple navigational aids might be erroneously making an approach to the base!