If the Germans achieved their objective of capturing Antwerp (extremely unlikely, but not impossible if everything goes perfectly for them), it would put the British armies in a bit of a bind, being cut off from their American allies. But the Hitler's idea that the Germans could then destroy the British pocket was utter nonsense. They would have dug in and waited for the Americans to blast their way through the German bulge.
I agree with those who say that a more successful German offensive could actually have shortened the war, as the Germans would have suffered heavier losses in attempting to hold back the American counter attack than they did IOTL.
It obviously would have dislocated Allied preparations quite a bit (which happened IOTL, too), but the only result would have been a shortened war and perhaps great Russian gains than happened IOTL.