It seems like the USA has learned nothing from the results of its preemptive attack in IRAQ.  If attacked the North Koreans would respond, as would any country, and who knows where it goes from there.

The leader of North Korea is not crazy/insane.  Even if he were, he is certainly not suicidal.  The USA would respond to any nuclear attack on itself or its allies with devastating force that would flatten North Korea and send the dear leader to his reward.

The bark is loud but the bite is not.