During the cold war, the Soviet Union had about 12,000 Inter Continental Balistic Misiles pointed at us, and no one changed their way of living. Now North Korea may have 2 nuclear bombs and a ICBM that can reach the west coast and everyone is afraid.
I don't think that North Korea would start a war with the US, because they would be annihilated in 5 minutes.
I think that the US might be tempted to strike first, since it is us that has the most to lose. If NK sells it's atomic bombs to terrorists, that would be very bad for the US.
Knowing that the US may strike first, North Korea has a couple of nuclear bombs pointed at us that they would use to defend themselves.
Thats what makes North Korea more dangerous than the former Soviet Union.