I hear ya. I don’t feel comfortable talking about spoofing from an op sec perspective. But true spoofing is far more complex to achieve. One easy cheap spoof solution that has been observed in the Middle East and reported in the open literature is simple gps repeaters (seen by a receiver on the international space station) If a receiver picks up a repeaters signal because locally it is a stronger signal, then the receiver thinks it is at the repeaters location. Without some smarts, this would certainly mess up your nav solution. But of course, if every receiver that gets spoofed by this technique is reporting to location of the repeater, the repeater is easily targeted.
When WWIII comes, the first things to go are all the satellites.