Again, any 'tit for tat' comparisons of this nature do not, by any objective measure, make N-K the greater villain.  That's not to say the situation with N-K is not concerning, but their militarism doesn't give the USA licence to act as the world's policeman, at least not in the eyes of the other super-powers.   Given what is at stake, they are better to err on the side of caution.