For what it’s worth:
Some folks associated with the Bulletin of the Atomic Scientists examined the trajectories of recent Nork ICBM test flights, looked at the presumed performance of the motors and propellant, and have concluded that the Hwasong-14 “ICBM” is a “sub-ICBM.” One of the authors of the study is a long-time critic of missile defense systems, so YMMV.
Even if the missile was a full-up ICBM capable of lobbing to New York City the kind of nuke the Norks could actually build, I would not bet large sums on the missile working as advertised in operational practice. That said… Lil’ Kim seems like a nut. Give him a weapon that will probably fail and tell him it’ll probably work (and I imagine his underlings will say what they think they need to in order to avoid the firing squad), and who knows, he might decide that The Stars Are Right and it’s time for his apotheosis via nuclear fire.
I’d be less sanguine about the chances of success for a missile like this lobbing a nuke *over* the US. A few dozen kilotons a few hundred miles up could wreak a whole lot of havoc via EMP.