Apparently you are not aware of the US anti-missile defenses. The THAAD system, which is deployed in SK, will take out their missiles, of which NK has very few. IF, by some miracle, the THAAD system does not take out one of their missiles, the Arleigh Burke-class USA destroyers, which are "parked" east of NK, will shoot down the missile(s) with their Aegis anti-missile rockets, THEN, if by some INCREDIBLE luck a NK missile gets through, the anti-missile defenses in California and Alaska will shoot the missile down upon re-entry. 
So rest well - NK is is a peanut in comparison and will eventually back down, as the world knows Trump is not to be fooled with.