acording to wikipedia the us has bunker busters capable of pentrating 6 meters of reinforsed concret. hell, the sixty year old grand slam could knock through 4.5 meters of concret.
so go back and do your sums. how quick do you think the us could knock out the most advanced bunker busters? it took only a month to job together one, and im willing to bet production could be ramped right up.
not to mention that soul will be the first target, and once that be redused to dust, the very first action i suspect, rather then something coming in time to be busted, the super fortifed line will be useless, subject to massive bombing camgains, and basicly screwed. the us can circmvent the main lines if needs be, and have proberbly considered it
ie. you just being hyperbolic, and i suspect, without knowing everything the us miltery knows, massively wrong.