A strike would not originate from North Dakota -- it would come from stealth bombers right on top of their artillery forces and command and control infrastructure, as well as from nearby boomers (ctf134) launching at a pace of a dozen warheads per minute, per boat, throwing mk-4/5's with recently upgraded fuzing systems.
When the LEP is complete, they will be GPS guided and accurate enough to destroy hardened targets from kinetic energy alone.
If the DPRK threat continues to escalate, and the US were concerned enough, F-35's could be upgraded with B61-12 harnesses, adding a nuclear stealth armada with pinpoint-accurate weapons to the arsenal. US fbm's are also not equipped to close to capacity due to arms control agreements. During initial flight testing, maneuvers consistent with deployment of 14 warheads were observed, meaning an fbm could deploy 336 warheads.