The Germans don't listen to Bulow and do better at Mons, possibly defeating the British sapping morale and allowing the Germans to keep to their timetable.
Joffre's command for the Southern option regarding the Marne is received delaying French forces a day giving the Germans even more of an advantage. The British continue to believe the attack is north of the Marne dividing forces and causing chaos. The Germans, with time and momentum, win the battle destroying the BEF and forcing the French back surrendering Paris. Perhaps this drives a wedge between British and French forces as the former feel they were used. Morale for the Entente hits an all time low, the French lose even MORE of their industry, and the Germans gain their Channel ports putting pressure on the RN.
By 1915 perhaps the British focus on peripheral theaters rather than the Continent, the French sacrifice hundreds of thousands in futile counterattacks to desperately regain their capital, Italy stays neutral, and the focus of Germany turns east leading to increasing pressure on the Russians. Maybe Russia breaks by 1916, the French Army collapses, and the UK settles for German colonies.