POD: Kaiser Wilhem is convinced by Bismark that an alliance with Russia is more valuable than a potential alliance with Britain and actual alliance with Austria-Hungary, and the Reinsurance Treaty continues.
(This is probably the follow-on from some earlier change, but it's the important end-result.)
Austria-Hungary quickly forms an alliance with France, and with her two greatest rivals part of the opposing alliance, Britain follows suit. The Italians are either German-friendly neutrals (if cautious) or allies (if aggressive), depending on how well they think they can protect their coastline. The assorted Balkan states join Russia, seeking to expand at the expense of Austria-Hungary. The United States quite happily sells to anyone with money, while Japan is already allied to Britain and the Ottomans happily sit this one out and work on strengthening and modernizing.
My first thought is that this should prevent anything closely resembling an alt-WW1, as Austria-Hungary is surrounded on three sides by hostile powers, unable to effectively help set off the Balkans powder keg. There's still too much tension in Europe to be held off forever, though, so something's going to give at some point - and I'd guess it'd be Austria-Hungary suffering from it, with three powers looking to expand at its expense.
Thoughts?