The moral of the story is to read threads more closely
9/11 investigators premise is still wrong. The naval blockade & the horrendous casualties made a German defeat inevitable irrespective of US involvement but it would have probably happened in 1919. The British & French victory in the 1918 spring offensive was very much the last straw for the Germans. They only have the man power for defensive operations after that.
That's not to say mutual exhaustion would not have ended up with some form of compromise, but that always struck me as unlikely. 1917 was the shift, with the Royal Navy finally conducting proper convoying operations, thus dramatically reducing the effect of the UBoats. Of course, if we're postulating a no-US entry, then I would argue you have to also go with a no-Unrestricted UBoat Warfare.
Into 1918 the British were ramping up tank production, and the plans for available tanks in 1919 were pretty impressive...I wish I had the figures with me, but we're talking thousands, with a sizeable (possibly majority?) being supply tanks.
Still, Spring 1918 would have been harder going without a load of fresh divisions available to plug some gaps. Then again, would Lloyd George have pulled strings to hold back on replacements without the US manpower around? Survive the spring offensives and Germany loses.