Is inertial guidance really that hard? We did it with 1950s tech and unlike rocket technology, the tech used in guidance has become much more accessible and accurate. Toys have fairly accurate gyros in them now.
Besides, how accurate do they even need to be? The capability to land a nuke on US soil from space is probably good enough to get people to the table so they can blackmail some more free stuff out of functioning countries.
I'm no expert, but it seems like this is a clear message they are basically there on an ICBM. Meanwhile, their people are starving, they can't keep the lights on and they are run by a cult of personality. Perfect.