The US can invade North Korea , but if they do, will the outbreak of World War 3 , North Korea is a country bordering Russia and China. The Korean missile can not reach the US, but they can reach japan and south korea , and if they make a massive nuclear and chemical attack , it's over for her 2 countries, only Russia and the USA have means has resisted a massive nuclear attack. In addition, USA crush North Korea , which caused a famine going on north korea, and all will flee refugee in China , a wave of refugee y 'will sn how syria and iraq , and China no way to contain a wave of immigrajation they are already 1 billion.