I was wondering if the ground strap can also protect the electrical/electronic parts of a car when a lightning strikes it.
No, That ground strap will provide a path to earth, it however does not influence the route the energy will take, let alone any induced voltages on harnesses routed near the body of the car
No. The metal body and chassis of the car will act as a Faraday cage and offer some significant protection of the electronics and people inside the car, but a strap that flaps around under the car will have a negligible effect on anything that has to do with lightning strikes.
The strap might help slightly with the kind of static electricity that gives you unpleasant zaps when you enter or exit the car, but even that it cannot do very effectively.