The shape of the Earth has nothing to do with the shape of its gravitational field, not from a distance. The mass of a body effectively behaves as if it's all concentrated at the center of mass, because the pulls to either side of it tend to cancel out. The spacetime curvature, as I said, is a result of the gravitational acceleration affecting an observer's measurements of distance, direction, and time. That would be true whether the object generating the gravitational field were shaped like a sphere, a cube, or a giant sousaphone.