The real concern should be remote-exploitation (e.g. via radio transmission). Someone will discover an exploit and publish it online.

The exploit will go un-addressed until government-owned vehicles start getting disabled. Then, governments will coerce manufacturers to turn disable the kill switch in all government cars. But that won't apply to person cars of government employees/officials, nor the cars that deliver stuff to government buildings.

Whoever wrote the kill switch provision was probably well-paid for their lack of foresight.