and if it happens ? so what?
They can hit us, we can hit them.
Weather they can or cannot hit us (if they tried) is doubtful.
From
Shutting Down Hostile ICBMs (MILITARY TECH):
While the war on terror has been grabbing a lot of public attention, the United States has quietly been in the process of neutralizing the missile arsenals of China, North Korea, and even Iran. This is probably one of the most important stories concerning the strategic balance, yet one of the least covered.
Prior to the attacks of September 11, 2001, the United States withdrew from the ABM Treaty (which it had signed with Russia in 1972), and began development of a national missile defense system. Research into missile defense had begun in earnest in 1983, but after withdrawing from the ABM Treaty, deployment was possible and became a priority.
The first phase of this deployment has covered the Pacific Rim, specifically with an eye towards neutralizing China's ICBM force. This is understandable, since on two occasions, Chinese generals have been quoted as having threatened to use nuclear weapons against the United States. The Chinese ICBM and SLBM forces are both very small (24 DF-5 ICBMs and 24 JL-1 SLBMs total). China's future plans for their SLBM force will center around two Jin-class SSBNs (the Type 094), each with 16 JL-2 SLBMs. China hopes to get as many as 60 ICBMs by 2010.
The North Korean missile threat is somewhat more different, and easier to deal with. Japan and the United States are both fielding the SM-3 missile, which has already proven it can intercept incoming ballistic missiles. The SM-2, also in use by both the U.S. Navy and the Japanese Maritime Self-Defense Force, recently carried out a successful intercept of a ballistic missile in the terminal phase. Both Japan and the United States also use land-based Patriot PAC-3 missiles. The result is a multi-layered system that will be able to blunt any North Korean attack.
These systems are not at the point where they can stop every inbound missile. The thing is, they still provide a deterrent against launching attacks – because a country that does decide to launch missiles at the United States or any of its allies protected by a missile defense shield will not know which of its missiles will fail to reach their targets. This uncertainty increases as the United States continues to deploy more ground-based interceptors, and looks into more systems. Ultimately, the uncertainty about the success of an attack created by the deployment of missile defense systems combined with the certainty that an attempted attack will bring a response, will be one of the biggest reasons for a country to decide not to push the button.
– Harold C. Hutchison