I don't know why anyone was ever worried about Korea before. Despite having been invaded by the Mongols, Chinese, Japanese, English, Americans, Russians and a few others over the course of the last 1500 years, Korea has never invaded anyone. Not even once.
As a matter of fact they have pursued an isolationist policy for about 300 years. If the USA, UN, World Bank and the rest of those set on global empire would simply leave them the fuck alone they'd spend more time growing rice and less time building missiles.
And here is what the media isn't telling you: IF that missle really did go 2,111.5 kilometers (1,312 miles) up http://www.cnn.com/2017/05/15/europe/north-korea-putin-russia-missile/ then YES THEY CAN HIT ANYWHERE IN THE WORLD. You see, they only needed to go up 99 miles to achieve low Earth orbit. https://en.wikipedia.org/wiki/Low_Earth_orbit
As Putin says, "find peaceful solutions."