Most of the Iraq and all of Afghanistan is more than 100 miles.
While 90% of North Korea and 60% of the Chinese population is within 100 miles.
That said, this is a first generation rail gun. Larger guns, with longer ranges, will be coming.
Right now, I would presume that the 100 mile figure is not the ballistic range, which should be considerably more at those velocities, but rather effective range for retaining enough kinetic energy to dispense with a warhead.