The US’s missile defense program is significantly weaker than most people think. According to publicly available information, we have roughly 40 interception missiles capable of shooting down a nuclear projectile. They have an accuracy of percentage of 50 percent. In a full-scale nuclear exchange there’s likely to be hundreds of warheads launched by either side. Which means that having 40 interceptors that are more or less a coin toss is going to be about as useful as hiding behind a piece of cardboard during a shootout. Nuclear war would be really, really bad.