The US ground missile defence in Alaska is aimed at Russian and Chinese rockets. Not only does the US missile defence system make it harder for rockets to fly, but it can also shoot them down.
According to the Missile Defence Agency, the anti-missile defence, the defence is directed against North Korea and Iran. "US military ballistic missile defence policies have sought to protect the homeland against a long-range missile strike from states such as Iran and North Korea, but not major nuclear powers Russia and China." https://www.armscontrol.org/factsheets/usmissiledefense