What's your definition of "threaten"? North Korea cannot win an all-out war with the US. But it seems reasonably probable that at some point in the decades to come, they'll acquire the ability to start such a war by hitting the US mainland with one or more nuclear missiles, potentially killing millions of civilians in one blow, in a catastrophe utterly unprecedented in world history - not to mention what they could do to South Korea and other nearer countries today. And while their leadership probably isn't crazy enough to actually start a war, they're pretty damn crazy. I consider that a threat.