Germany was by no means unified in the strategy best characterized by the Schlieffen Plan if you are looking to change things up. Throughout the latter half of the 19th and into the early 20th century the two schools of thought were roughly translated into English as the elimination strategy and the attrition strategy; I forgot the fancy German terms. It was a debate that went on for decades that only tipped into an "elimination strategy" over the late 1890's to the adoption of the Schlieffen Plan in 1905 and only truly ended in 1914 when Germany committed to the Schlieffen plan in the opening phase of the war.
The Elimination Strategy was what Germany eventually adopted under Schlieffen. A single grand maneuver meant to completely defeat an enemy in a single campaign. It called for catching the enemy armies out of position and through aggressive maneuver seizing key locations and breaking the ability of the enemy; in this case France; to wage an effective war. Proponents of this mainly used the Franco-Prussian war as their example seeking to emulate it in a modern war.
The Attrition Strategy on the other hand called only for tactical offensives to gain needed defensive terrain and necessary resources both to help Germany and deny them to the enemy. There was no expectation that the war would be finished in a single campaign season and the idea was to use a mix of local superiority, tactical grab and hold offensives, and extremely in depth defenses to wear out an enemy force and bring about a peace conference. Proponents of this strategy used Frederick the Great during the 7 years war as an example of how this strategy could be effective. As late as the 1890's the German General Staff felt this was the better strategy to deal with a Franco-Russian alliance.
Interestingly Moltke the Elder by the late 1870's felt that an Elimination Strategy was unfeasible against a Franco-Russian or Franco-Austrian alliance given the fortifications of France and introduction of widespread conscription in France and Russia. It wasn't until the late 1890's that Schlieffen felt that an Elimination Strategy against France alone would be feasible by going through the low countries and it wasn't until 1905 itself that it was felt possible to do it when France was apart of a Franco-Russian alliance and even than he went through multiple variations of elimination and attritional strategy being war gamed before ending up with the Schlieffen Plan as we know it today. It was by no means even after 1905 a universal belief that the Imperial German Army would be able to pull off such a maneuver against France and Russia.
In this case with overt US support of Japan during the war the impression of Russia as a broken power would be lessened perhaps just enough that Germany would pursue a more limited offensive against France than dig in deep and throw themselves against Russia. Proponents of this strategy could point out that in the Western Front it would be Germany alone while in the Eastern Front Germany would have the Austro-Hungarian army along with them. Moltke the Younger already hedged his bets from the Schlieffen Plan when he became head of the General Staff after 1906; weakening the western armies and strengthening the eastern ones; and a slightly lesser belief in Russian weakness could see him wholesale change plans from a France centric elimination strategy to a Russian centric attritional strategy.
To be clear Germany adopting an attritional strategy would also be a Germany that doesn't expect to be able to "win" in the sense of German armies in Petrograd and Paris. Instead the strategy would be to bleed out the Russians enough and make French offensives futile enough that a peace conference would be held ideally with German armies on foreign soil and no foreign armies on German soil.
Ultimately it is up to you how you want Germany to develop but don't think you must stick with something resembling the Schlieffen Plan for "realism sake" as it wouldn't have taken much for the attritional strategy faction to come out on top and a Russian centric war plan to be adopted. Even something as simple as a more confident Britain making it clear to the German government that a violation of Belgium's neutrality was a red line in the lead up to a war could push the plan away from OTL.
