Even though this is a mid-course interception, it's critical that we contrast it with America's GMD (ground-based mid-coure defense). GMD is targeting ICBM payloads, which travel faster and are more likely to have countermeasures. GMD is still unproven for targets without homing beacons on realistic trajectories. Long and the short of it: this doesn't mean America could successfully intercept incoming nukes from North Korea.