I also understand that those nukes regularly get deliciously close to their targets (100 miles or so) (delicious from the point of view of the attacker).

I stand by my assertion however: to be explicit, for the same energy budget, it is quicker to hit a target from the ground half-way around the world from the target than it is to hit the target from orbit even if the satellite is directly above the target. The exception to that is laser weapons because a laser beam has no momentum whereas all the "strategic" nukes in the US arsenal weigh at least 200 lb, which is a lot of momentum when moving at orbital speed.

(Also, it is vastly cheaper to maintain infrastructure on the ground than in orbit.)