And you won’t be able to drive your cell network connected car… making logistics impossible. It’s a big enough wartime issue there ought to be a regulation that the cell device should be able to be “pulled” and the car defaults to “fully enabled”.
Many cars have something similar (remove SIM card, cut antenna) that allows them to keep working without connectivity
Incidentally, this link recommends termination resistors, which I think are the better answer if there's a suitable connector (which I imagine is the case for most cars). If it's not terminated, I believe it can still pick up a nontrivial signal.