The U.S greatest threat

i believe that the greatest threat to the U.S is North Korea. North Korea has built their supply of nuclear weapons and other long range weapons. North Korea has often said that they would attack any country that messes with them. what if someone does? i don't think a nuclear war would go great right now. Too many people would die and with the way the economy is it would forever fall and may never get back up. North Korea is our greatest threat.