The Minuteman III (the backbone of the US ICBM fleet) has a listed CEP of 200 m. The Trident D5 has a CEP of as low as 90 m, but it's an SLBM not strictly an ICBM, and it varies depending on range.
The CEP figure represents the radius of a circle where there is a 50% chance of the bomb landing within that circle. The CEP figure is basically 2/3 of a standard deviation.
I suppose I should have said "some". Anyway, when looking for the state of the art, we should look at the best value available, rather than the average or typical. The Peacekeeper missile lists a CEP of 120m, although it's now retired. As for Trident, with a 11,000km range, I think we can put it in the same category when looking at reentry accuracy.
In any case, accuracy is gated by navigational accuracy, not so much guidance, as long as your initial aim isn't too bad. ICBMs have a 100m CEP because they're using inertial navigation all the way. Switch to GPS and you'll have no trouble doing better. In the context of SpaceX, getting the rocket to within a few hundred meters of the landing pad is perfectly fine initially, because it can then maneuver to the pad more precisely.
The CEP figure represents the radius of a circle where there is a 50% chance of the bomb landing within that circle. The CEP figure is basically 2/3 of a standard deviation.