US citizens are the ones that shouldn't be scared but the poor innocent North Koreans.
The US is always up to date on war technology and have tons of allies. North Korea is in a bad place because they don't have US money, technology or allies. China is a partner with Korea but they are not backing them going into this war.
Also you have to take in consideration there leader is young and reckless. There is a reason that his father after all these years never took a step towards the US.
I mean look at the difference between North Korea and South Korea from the sky at night.