what has the U.S. done in response to decades of NK counterfeiting our currency?
That is an excellent question. It is an act of war and the Norks have been doing it for decades and getting away with it.
They will get away with this, too. Uncle Sam has become Uncle Grovel and they know it.
They may try and shut down our electrical grid next just so we can freeze and starve in the dark just like them. They quite likely have the capability to do it right now.