The problem for the Entente is that they have some serious blows to take or have already taken them.
Those are the Russian Revolution that signals an out of them is probable, the financial and following supply problems will be serve without the USA to loan and last but not least the Nivelle Offensives brought French morale down to the breaking point.
So all in all the Entente without the USA in is in dire straits, if they know it or not. Same for the Germans, they may not realize the precarious situation the French and British, here it is the loss of oil for the fleet coupled with the lenghtening of supply routes, are in.
So what can the French and British do? Another offensive is Imo not realy in the cards, as the French morale will probably be worse then in OTL, no USA morale boost here. So what can they do? The situation in France may detoriate rather fast, the naval situation is not to roosy, Escorts need oil and the Battlefleet too, couple that with more and more preasure to reopen neutral Europe to trade and that will likely flow through to Germany to lessen the blockade. And suddenly a fast peace may be the "best" they can hope for, before the French (may or may not) collapse and the British face too much deprevations on their merchant marine to supply the civilians. Here the Admirality saw the limit at 400.000 tonnes per month and the Germans were doing that an more AFAIK.
So would they chance a repeat of 1871, with revolution in France for the long shot of one last hurray? I doubt it but it could happen.