Kim Jong-un, as leader of North Korea has sufficient evidence in history that America has blasted his nation in ways that were not pleasant. During the Korean War, the city of Pyongyang was obliterated with death to thousands of innocent people. His mind is still locked in the past rather than seeking a way to allow the present to help North Korea develop into a modern nation. For nearly a month each day witnesses another outburst and threats to demolish South Korea or hit the American shores. Threatening attacks on Hawaii or Midway may impress North Korean generals but they pose a risk of having thousands of innocent people die due to temper tantrums.
The US has flown two nuclear capable B-2 stealth bombers to South Korea in an effort to show that America is capable of devastating actions against North Korea. Most probably the boys in North Korea will simply send planes into the air to prove they also can blast away.
Perhaps, Kim Jong-un wants to prove to generals that he is a man of action by uttering words of action. Hopefully, he will never have to back up words with action–neither will the rest of humanity!