On the contrary, it is crucial here.
Let the gravitational attraction of the Earth on the car be W.
In the frame of the rotating Earth you have to consider the centrifugal and Coriolis forces:
https://en.m.wikipedia.org/wiki/Coriolis_force.
The centrifugal force, ##mR\Omega^2##, points up. Here, R is the radius of the Earth and ##\Omega## is its rotation rate.
The Coriolis force is given by ##-2m\vec\Omega\times\vec v##, where v is the velocity of the car in the rotating frame.
If the car were going West to East, this would also point up, giving a net upward force in the rotating frame of ##3mR\Omega^2##. To an observer in that frame, the car has an acceleration ##R\Omega^2## towards the Earth's centre. For all this to add up correctly, the normal force from the ground would have to be ##W-4mR\Omega^2##. Back in the inertial frame, the car's speed is ##2R\Omega##, so the centripetal force is ##4mR\Omega^2##, giving the same result.
But here the car is going East to West, so the Coriolis force points down, and its magnitude is ##2mR\Omega^2##. Gravitational force plus centrifugal plus Coriolis gives a downward total of ##W-mR\Omega^2+2mR\Omega^2=W+mR\Omega^2##. To the observer on the ground, the car's acceleration is the same as in the W to E case, so the normal force must be just ##W##. In the inertial frame the car is stationary, giving the same result.