its mostly a lack of knowledge. There is no kill switch etc.
The F35 does come with an international support network, which could in theory be turned off, so once you used any spare parts of your own, you will find it hard to get any more.
here is no way the UK or anyone else would buy a system with a built in kill switch. But also a reason why the UK still has 2 different fleets of aircraft, one american, and one British or European.
But then look at switzerland, with the Gepard ammo.
Most US aircraft have 2 or more computer operating systems unrelated to each other and manufactured by different companies as a safeguard to any sort of hacking.
This "kill switch" story is just manufactured click bait.