do you think north korea will nuke america?

That would be a blunder a country will ever do. Nuclear attack is not like those attacks where only soldiers sacrifice their lives, those bombs have the ability to devastate the whole nation or even continent. Moreover, no one survives in the end, so if North Korea would drop a nuclear bomb on USA, or vice versa, its obvious the one who attacks first would be at advantage as the other part would be completely destroyed!! It may happen that no one survives to retaliate. God, it should not happen, both mighty nations would suffer badly.