Are satellites moved to keep them aligned? Are they at risk of becoming unusable from the small, but measurable changes to Earth's rotation?
The very small changes in the Earth's rotation rate pale in comparison to the much larger perturbations that geosynchronous satellites experience from the Earth's non-uniform gravitational field, gravitational perturbations from the Moon and the Sun, and non-gravitational perturbations (radiation pressure) from the Sun.
In addition to the above, the ability of a geosynchronous satellite to hold its position is imperfect. Because of those perturbations and the not quite perfect control, geosynchronous satellites are assigned a longitude band in which they must operate, as opposed to exactly hovering over a specific point. The tiny changes in the Earth's rotation rate is yet another perturbation that geosynchronous satellites must accommodate to stay within their assigned bands, but this is a tiny perturbation, essentially in the noise.