Huh?!? The United Nations has been in a continuous state of hostilities with NK since its Security Council Resolution 84 of July 7, 1950. The armistice was signed by a U.S. representative of the United Nations Command (UNC).
There has been no U.S. Declaration of War against North Korea.
You are correct that Congress did not declare war
Hence the term Police Action, per
United Nations Security Council Resolution 84
Congress DID formally appropriate funds for war actions however
and continues to fund emplaced soldiers, war making materials, and barricade actions