In the case of a car moving with uniform velocity, Newton's first law states that the net external force acting on the car is indeed zero. This means that the forces acting on the car are balanced, resulting in no acceleration.
When it comes to canceling out friction, it's important to understand that friction is not an external force in this context. Friction is an internal force that opposes the motion of the car, and it is caused by the interaction between the car's tires and the road surface. It is not an external force acting on the car.
In the absence of any other external forces (such as a headwind or an inclined surface), the forces that balance out the friction are the internal forces generated within the car's engine. The engine produces a forward force, typically transmitted through the car's wheels, which counteracts the frictional force and allows the car to move with uniform velocity.
To summarize, in the case of a car moving with uniform velocity, the net external force is zero according to Newton's first law. Friction is an internal force, and the force generated by the car's engine counteracts the frictional force, allowing the car to maintain a constant velocity.