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,
It was a plane. 148. The discussion is over.
And in turn I would suggest you analyze this with a view towards what makes sense. If you are an opponent of the United States why would you advertise your abilities and highlight your opponent's weaknesses? If this was, in fact, what you say it was then the Pentagon now knows that the Chinese can do it and that the west coast is vulnerable. It would stand to reason that they would take steps to prevent it from happening again. So in your scenario the Chinese have just taken a potent military advantage and tossed it right into the dumpster. How much sense does that make?