The article omits numerous things. First of all, we've got more than just the 18 missile interceptors in Alaska and California (plus one "test" interceptor in Alabama). That's just the land-based part of our National Missile Defense system.
We've also got Aegis destroyers and SM-3 anti-missiles at sea. At least two of those systems are off the coast of North Korea at this very moment.
In addition to all of that, we've got one Boeing airborne laser interceptor...as well as armed UAV's that can take out enemy missile launches in the first 30 seconds (the time it takes to reach Mach 1) of firing. These systems can down enemy missiles while they are still over enemy airspace.
Put together in sum, those 3 phases of our missile defense constitute a viable, if not perfect, defense system.
Also, it's no accident that we've put 18 land-based interceptors into operation so quickly. That happens to be the exact number of Chinese nuclear ICBM's at the moment.
Thus, we've fundamentally altered their military options and calculations from this time 5 years ago.