It brought matters to a conclusion faster than would otherwise have been the case (six months? A year?) and so saved a considerable number of lives, both on the Western Front and also in Germany where the impact of the blockade on the civilian population was considerable. By the time the American reinforcements actually arrived, the lunatic gamble that was the Ludendorff Offensive was already being pushed back and from that defeat there could be no recovery, but there's a reason why it was launched when it was in the first place.
Agreed, as my understanding of the offensive was always that it was a desperately rushed move to try to deliver a knockout blow before American troops arrived in Europe in serious numbers.
