IMO, the only way a war between the USA and North Korea would happen, would be if the USA made a pre-emptive strike on NK. Nobody, no matter how doo-lally, would openly attack the most powerful military force on earth - the North Koreans know they would be squashed like a bug underfoot. They also know that if they deliberately attack a close ally of the US - they will be wiped out - and nobody is that crazy. The danger to Americans is much more likely to come from some terrorist attack - a dirty bomb, or pollution of the water supply, etc.