logical fallacy, at least the way you phrased it.
If we put your argument into syllogistic form it would be something along the lines of:
A. The U.S. has a much larger arsenal & army than North Korea
B. Some/many countries fear the U.S. more than North Korea's army & arsenal
C. Therefore we have nothing to fear from North Korea's ICBMs & hydrogen bombs despite their threats to use them against the U.S. and the U.S.'s allies.
Even if one were to accept your first two premises, your conclusion does not follow. It is the logical fallacy known as a non sequitur:
https://rationalwiki.org/wiki/Non_sequiturEdited by JeffB at 10:29:20 on 10/05/17