Is it possible that Germany could have been forced to dissolve into it's constituent states (Prussia, Hanover, Bavaria, etc...) as a peace condition following World War I? And, perhaps, the states are forbidden from uniting for, say, fifty years?
Possible? Yes, but not without the Entente marching triumphantly into Berlin. Which means at least another year or two of warfare (and appropriately higher casualties), as well as cementing German (and the population would still consider themselves German, regardless of the division) eternal hostility.
I'd say Germany would re-unify and try for revenge, unless the Entente is willing to maintain a lengty and expensive (both in manpower and resources) occupation of Germany, as well as repeatedly invading to keep the various newly formed states from causing trouble. Considering French hesitance to act with lower casualties than what they would suffer TTL, I can't see them being willing to do so.
Which means Germany re-unites and pushes for revenge, although with a very different focus.
Even if none of the states falls to Communism, I could see Stalin being happy enough. The Soviets were perfectly content to cooperate with the Weimar Republic to outright break the Versailles Treaty, they'd probably do the same TTL, using Germany as a proxy to drive away attention from Stalin's own expansion into Finland and the Baltics (and, potentially, Poland).