That nobody saw. So tell me this, if the missile went over the entire country and landed a thousand miles into the Atlantic then why the need to launch from 40 miles off the west coast? In your scenario they could have launched from a thousand miles off California and hit every city in the U.S.
To show they can approach undetected by our defences and increase the fear factor to the threat.
This sits better with a highly focused EMP attack (still nuclear but better guided from closer range and removing much of our capability to survive financially). No intent to hit ALL cities anywhere. Multiple warheads, selected cities for maximum economical damage. West cost launch for west coast targets, the New York one for the east Coast pinpointed city targets.
It was not a mass attack but a carefully pointed warning to us to not cross certain financial lines - like the Fed “easing” plans.
Also this close range “debilitating” launch would prevent our retaliatory attacks while long range launches would have been picked up and possibly provide us enough time to launch prior to being hit.
And lots of things can happen unseen in the middle of oceans even “busier” ones like the Atlantic and very easily in the vastPacific.
You usually defend the Obama regime but analyze this with the neutral hat you appear to have donned for the discussion,