I'm not totally sure, but i guess the war would end in favor of germany and it's allies.
Without the American intervention Germany might be able to reach Paris since it haves full superiority on the western front and as said by many the french army was nearly collapsed due to mutinies. without the russian front IF AH and Bulgaria manage to resist enough until the french capital.
A possible peace outcome would be:
-Germany keep Alsace and Lorraine and france renounces every claim on it
-Brest-litovsk treaty acknowledged from entente
-AH keeps gets control over Serbia and starts it's federalist reforms( or else explodes few years later)
-Bulgaria gains control over Macedonia,pirot(from serbia with bulgarian pop), takes back dobruja from Romania with almost all the sea coast( control of southern river of danube, Romania northern) and occupies Salonika from greece
-OE takes Dodecanese from Italy and the libyan colonyback
-since england hasn't been touched on any territory it would basically whitepeace.
-france would pay partially or all the German debts, this would probably lead to communist france
-Italy loses the colonies( all freed while dodecanese and libya to OE) and pays debts to AH, thus leading to Mussolini or another commie nation
-Serbia loses the gains from the balkan wars and becomes part of AH
-Greece loses the north but keeps it's mainland since the minor partecipation
-Romania for it's betray( gifted with bucovina from AH) would give back Bucovina, Deminilitarize and pay the bulgarian debts while losing almost all the sea access and it's ploiesti oil deposits would be controlled from CP
-Russia as OTL
-Japan keeps some of the island taken from germany
with this outcome the worst scenario would be a french commune join comintern and helping the spanish civil war( no franco ?) while AH doesn't reform and explodes ( germany is busy recovering so it doesn't help) and Bohemia,AH( literally austria and hungary), Serbia, Bosnia,Croatia,Transilvania are formed while poland(german king) takes something. Italy gets Benito as OTL but no colonies or ethiopian war but perhaps joins the CP with apologies for betray to kaiser willy.UK faces a de facto defeat and struggles to recover, maybe oswald mosley could gain more popularity but it's difficult.
it's similar to kaiserreich but Instead it might end with a germany with CP(italy, bulgaria, OE, what is left of AH and the puppets) against spain,france,ussr.