FHSS[1] has made jamming difficult in US military communications for decades. It doesn’t make it impossible but jamming the entire spectrum is nearly impossible at scale for almost everyone. At best it would affect small areas until the US sent rf seeking missiles (HARM are designed for this) at the jammer source. Also note that modern satcom like Starlink uses AESA digital phased array antennas much like a F35’s radar. It’s so much more complex than legacy analog stuff.
It’s easily possible to jam a frequency spread signal from a satellite, assuming you can get the directionality right (i.e. you need to be in the beam of whoever you’re trying to jam, or you’ll need even more power to overcome their receive directionality, which is never perfect).
Signal strength (satellites are power constrained) and distances involved are tough.
GPS uses frequency spreading too, and locally jamming that (even the military version with a secret/unpredictable spreading code) is trivial, for example.
US military gps is encrypted and heavily used FHSS. It is jam resistant, and can’t be jammed without significant expertise and know how.
Russia has some of the best EW chops in the world (after the NSA perhaps), and they struggled to successfully jam Starlink after some defensive work was carried out by SpaceX. They use Starlink in the “sea baby” USVs that attacked Crimea just last night.
GPS uses DSSS, not FHSS. The military version has a higher processing gain than the civilian signal, but it can still be overpowered by sheer signal strength.
I'm not saying that that's trivial against moving targets in a large area (especially if they can use directional antennas), but it's still very possible. GNSS jamming is a big concern of the militaries of the world, and there's currently somewhat of a renaissance of high-precision inertial navigation systems as a result.
Jamming a stationary satellite terminal, if you can get reasonably close, doesn't seem harder than cutting a fiber (although as a sibling comment has mentioned, jammers have the nice property that communication is restored once they're disabled, unlike damaged cables, so maybe the two can complement each other?)
[1] https://en.m.wikipedia.org/wiki/Frequency-hopping_spread_spe...