https://www.rtl-sdr.com/using-a-hackrf-to-spoof-gps-navigati...
The same principle is likely applicable to other standards as well, until the day they add encryption, which will probably need a lot of time and research to overcome the inevitable associated timing problems.
If doable at military level, the possible scenarios are catastrophic: country A launches say 5 test missiles, country B from nearby hidden submarine launches 5 much smaller and stealth jamming missiles. The jamming missiles approach the bigger ones then jam them into believing they're slightly off course forcing them to adjust, while in reality they're being slowly directed to country C. Of course any loss of control by ground base should be interpreted as self destruct by the missile, so it'd be near impossible to do it actually, but if other signals could be spoofed as well as positioning, then that would be a problem.