Supposedly by next year NK will have icbms which could launch a nuclear warhead to California. Me here on the east coast is safe, but there are 26 or so million people living on that coast who I am sure do not want to be at the mercy of that lunatic dictator. There are other countries that have the capability to hurt as just as much. The difference is that they are not fanatical like North Korea. Until the fascist dictator is gone (including all his descendants) North Korea will pose a threat. Even after they are gone, there will have to be a major political revolution and cooperation with other countries in order for them to not be a threat.
On another point, I think North Korea has showed just how powerless and useless the United Nations really is. When dealing with non-cooperative nations diplomacy and sanctions do nothing but to spur more hatred and make them more resilient. Military force is the only way to MAKE them understand and cooperate.