Our current policy is not to interfere with the capacity of Russian or Chinese missiles to devastate the United States.
Today’s newly destabilized world having resurrected the specter of nuclear war, it behooves us to plan for ways to prevent and defend against a ballistic missile attack. Technology is less a bar to such antiwar insurance than are the U.S. government’s illusions and assumptions. Rhetoric aside, U.S. strategic policy is still mired in a 1960s assumption: that the fear of nuclear destruction makes these weapons unusable, and in the illusion that this fear is shared universally.
China, which has threatened to nuke Los Angeles and has been upgrading its missile forces to do just that, builds islands in and claims sovereignty over the South China Sea. Vladimir Putin builds new missiles while promising to back future Crimea-like ventures with Russia’s nuclear arsenal. Both practice killing satellites in space. Iran builds nukes and practiced sinking a U.S. carrier. American policy has not banished the specter of nuclear war.
Source: How To Defend The U.S. Against A Ballistic Missile Attack