All military navigation systems are inertial, not GPS. They only accept GPS corrections within the error bars of the inertial system. As a practical matter this means that you can only make a drone deviate from its intended course by a few meters assuming you did a perfect job of spoofing the GPS.
GPS spoofing/jamming only works for systems that use GPS navigation systems; military weapons and systems have never used GPS navigation. Inertial navigation systems are spoof-proof.