NK should worry about the bombers they can’t see...
Exactly, this is a show of force. What's the old saying, rattling a saber makes noise, drawing one does not...
If anything, the message of these bombers is "we will end you." By that I mean, they represent the end of NK as a habitable zone. If NK were to do something stupid and launch a WMD at us, our territories, or our allies - we would use immediate retaliation to end the threat. Missile defense forces to knock down the WMD, and almost certainly sub launched MIRV'd systems to wipe every potential launch site. That ensures no further immediate attacks. But these weapons are limited in number and thus valuable not only in a monetary sense but in a strategic sense. So you only use them for extremely high value targets - preventing further attack.
That's bad enough - a dozen or so smaller nukes going off in NK. However, it is the bombers that represent the end of the world for NK. About the time the sub is achieving launch depth, the bombers are starting engines. A few hours later, after the dust and debris thrown up by the initial strikes has cleared, the BUFFs arrive overhead and systematically glass every facility in NK that ever had anything to do with their missile or nuclear programs, including military and "civilian" leadership sites. Picture a couple dozen more nuclear weapons going off - some of them big stuff for digging out bunkers and deeply buried facilities. By the end of the day NK ceases to exist and is rendered uninhabitable.
The bombers aren't retaliation, they are the final, permanent solution to the NK problem.
“NK should worry about the bombers they can’t see...”
You mean the 111 B-2’s (of the original order) that we never built because “peace was breaking out all over the world”?
I doubt Kim worries too much about our stupid decisions.