Considering the vastness of space even close to earth, I was thinking that within a couple miles of a satellite is very very close as well. The relative speed is pretty large.
How many of those nuclear ABM's were actually tested? I knew they used them in limited numbers, but I don't think I ever heard that.
All that said, I doubt we would have too much trouble coming up with a way to down satellites, but I agree it would be nice to have one in inventory.