Without American interference in 1917 the Central Powers had the war basically won when Russia surrendered. There was no way for Britain, France, and Italy to deal with Germany, Austria-Hungary, and Turkey at that point. France faced the trench mutinies in 1917, and Italy was on the brink of collapse. A negotiated peace at that point would probably have spared us the movements that brought about WWII - and possibly the Bolshevik Revolution later in 1917 as well.
Essentially true but the central powers were on their last legs as well. And neither side wanted a negotiated settlement. (well, OK, Austria did)