Initiative.
I propose that what little initiative the Germans had on Dec 16 was mostly gone by the the 19th or 20th, when Allied ground commanders met in Verdun and decided to fight the Germans on the ground of their own choosing.

The German 6th Panzer Army (PA) had been stopped cold in the North, the German 7th Army was making little progress in the south, mostly on the heels of the 5th PA's tail. Only in the center (German 5th PA) were Germans making any headway, essentially against no forces, since the US 106th Infantry Division (ID) had lost two of it's regiments and most of it's artillery.

The US 422nd and 423rd Infantry Regiments of the 106th ID were unable to manuever as the result of being on the wrong side of a river with insufficient bridging to connect them to the rear. They simply ran out of supplies and unlike locations to the rear, they were so far forward that significant supply depots did not exist where they were. The other divisions in the center (US28th ID, US 7th Armored Division) and the various cavalry groups were able to retire in good order because they were not positioned so that their ability to maneuver was handicapped like the US 106th ID.

The decisions to fight at Elsenborn Ridge, St Vith and Bastogne, certainly born of desperation, served their purpose of denying the Germans the initiative, slowing their advance and allow other Allied forces to prepare to fight in other locations. The forces in these area were helped by a better supply situation than was the 106th. The Allied decision not to go on the offensive along the length of the bulge until all forces were in place was a sound one. There were no large scale counter-attacks early on by the Allies. This allowed the Allies to fight using their strengths and capitalize on German weaknesses, when the weather cleared and the German attack was weakening.

From the 19th on, the Allies held the initiative, even though they were falling back in the center. It was an action akin to allowing a cow to through a chute at a slaughterhouse. The cow thinks is going somewhere safe, but we know better. Eisenhower's early efforts were to hold the shoulders of the bulge strongly and allow the Germans movement in the center, until forces could be marshalled to slow the entire German offensive.

That is pretty much what happened. Look at maps of the battle. The shoulders held and Germans went blithely toward their defeat at Celles on the 24th. It was there that Allies fought German armor on the ground of their own choosing and defeated them.

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Best Regards,
JW