What makes you think Article 5 requires consensus?
https://www.nato.int/en/what-we-do/introduction-to-nato/coll...
> if such an armed attack occurs, each of them, ... will assist the Party ... attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force,
"Each" and "individually" imply to me that even if the US decides they could meet their Art 5 obligation by sending a strongly worded letter to themselves, every other NATO member, invoking the right of collective self-defence, should forthwith assist DK with armed force.