Yes, but so much public safety relies on it, it is unlikely that anything would get turned off or noticeably disrupted. Airplanes rely on it. Big ships rely on it. Business relies on the GPS signals for timing critical electronics and financial transactions. I think that the coast guard shut down their Loran system many years ago, leaving GPS as the sole way to see where you are in a harbor in fog or at night.

If the military messed with it, it would probably be to disrupt missile targeting, in which case I suspect most of us would be happy they messed with it.

I needed to get some land surveyed over a decade ago. Met the land surveys on site. They were using GPS. They said that the section corner in county records was off by 0.07 feet, or else the marker had moved. I told them that snow plows had moved the section corner monument before, likely would happen again. I was surprised at their level of accuracy, but they were less than a quarter mile from the differential station that they had set up at the town hall.

That said, short range jamming and spoofing is common on the battlefield.

Speaking of fog, that is the reason I bought my first GPS over two decades ago. If you are paddling your kayak towards an island, and accidently miss it, you could have a bad day.