North Korea does have nuclear power, even nuclear weapons. Russia and the USA helped them develop nuclear power for things like electricity and etc, but they used that knowledge to develop weapons. (Really not too dumb an idea considering it's the only way to defend against a nuclear attack on your own country). That went against the deal Russia and the USA had with them. The USA not only pulled out of the deal however, but has been making a lot of threats and etc ever since attempting to control the production and any attacks or targeting of nuclear weapons in North Korea.

https://en.m.wikipedia.org/wiki/Time...uclear_program

A lot of tension has risen between the two countries over the years as a result. Now, it's coming to a head. North Korea obviously doesn't have as many nuclear warheads as the USA, but it is unknown what the exact number is and to what strength their weaponry lie (though I am sure there have probably been military operations sent out to find that out by now). Depending on those things as well as if and what active allies they may make should they choose to fire upon us, they could indeed be a threat. Even one "weak" nuclear warhead does a lot of damage, sending several strong nuclear warhead to the right places, could cripple us, regardless of if they have more than us or not.

Effect of nuclear weapons | Nuclear Darkness & Nuclear Famine - The Deadly Consequence of Nuclear War

The attack most feared is an EMP (electomagnetic pulse). It is unknown if North Korea has a nuclear capability of this nature, but countries such as Russia do. This type of thing would cripple us and allow another country to easily take over or kill us off, as it would wipe out all electronics and computer technologies. That would render us incapable of operating most of our vehicles, the military would be unable to fire it's nuclear based weapons, or any other weapon requiring computer technology. Our communications with the outside world would be wiped since our phones, computers, and televisions would be inoperable. After an attack like that, we would more or less be "sitting ducks".

Electromagnetic Pulse (EMP) Attack: A Preventable Homeland Security Catastrophe | The Heritage Foundation

President Trump has angered so many leaders, it is feasible to consider if North Korea decides to pull the trigger on us, Russia (the most powerful and most feared nuclear power in the world) or some other country with nuclear power may join in. Both Russia and China are big nuclear powers and both have been angered by Trump. It's a touchy situation, but I still have my suspicions about it all.