Let me just point out that satellites don't necessarily orbit around the world. They can be geostationary, and in fact they usually are I think. That is why you will find most US GPS satellites over the US, most Russian satellites over Russia, etc.

Also, signal disruption is already very common as a necessary precaution at sensitive times and places. I think many military bases and other sensitive places, like the Kremlin, have signal interference so they are very imprecise to target with GPS-guided weapons.