Internal and External Forces

What makes a car accelerate from rest?

Is it the force of the car's engine on the drive shaft or the force of its axles on the wheels? Or, is it the frictional force of the road on the car's wheels?

The drive shaft translates the internal force of the engine to the axles. The axles then rotate the wheels. The rotating wheels experience an external frictional force by the road and the car moves forward.

If there is no frictional force, say when a car is stuck on an icy road, the wheels will rotate but the car would remain stuck in the same place.

Consequently, it is the friction exerted by the road that propels the car forward.

Such forces that originate outside the system of interest are external forces. Only net external forces can change an object's state of motion.

Whereas, the internal forces originate inside a system and are exchanged within the parts of the system. They do not cause any acceleration.