Honestly, if you look at a brand new pool ball, that thing’s less round than the earth is. So it’s pretty spherical. There’s a difference between roundness and smoothness though and while the earth is mostly smoother than a billiard ball, it’s less smooth in the mountainy parts (Himalayas to sealevel and Andes to sealevel)
I know there’s a deformation due to spinning, what I’m saying is that this deformation is percentual less than that of the standards expected for the fabrication of pool balls. If you think of billard balls as perfect spheres, you should also think of the earth as one.