North Korea has successfully tested two intercontinental ballistic missiles and a nuclear bomb in 2017 with way more destructive power than those dropped on Hiroshima and Nagasaki. North Korea nuclear threats to U.S.A are very serious.

North Korea has conducted 14 nuclear test missile launches in 2017 alone. That includes 5 types of missiles.
  1. Hwasong-7 Er Scud
  2. Hwasong-12
  3. Hwasong-14
  4. KN-15 Pukguksong-2
  5. KN-17
And there is a new threat to the US every time there’s a new launch. United States keep working on making strategies for their defend.

How would US defend itself against North Korea nuclear attack?

Below is the infographic covering all the missile launches by North Korea in 2017.
Source: http://edition.cnn.com/2017/05/29/asia/north-korea-missile-tests/index.html