They very much could have won it, but they couldn't maintain the speed they needed, because allied command (attribute it to whomever you like) concentrated on restricting German movement via obstructing the bottlenecks (Bastogne being the best known). Even if the Germans had retaken Antwerp, they could never have held onto it long enough to accomplish their objective of starving the US and British (okay, and French) armies.
In a "A Soldier's Story" Bradley noted that the attrition rate of riflemen was enormous, but a massive mobilization was still going on that would have led to a large percentage increase in US troops in Europe if needed, even with the approaching denouement in the Pacific theater.
By the time of the Bulge, the entire southern coast of France was in US hands, opening up additional avenues for shipping in cargo. Ultimately, even a German victory would not have done more than delay the end, and even that wouldn't have been for long.
Sorry but you’re wrong. German generals knew the plan was hopeless and many of them wanted to concentrate all that armor on the Eastern Front. They knew once the weather cleared Allied air power would slaughter them.