All of the events you listed were critical in ensuring an Axis defeat by 1945. Pearl Harbor brought one of the world's greatest industrial powerhouses into the war on the same side as the other one. Kursk ensured that the Germans would never again have the initiative on the Eastern Front; But if you are looking for one single point where the entire course of the war was changed, then it would definitely have been at Stalingrad. The encirclement and destruction of the German 6th Army left the northern flank of the entire Army Group South completely exposed in the Caucasus, forcing them to withdrawal away from the oil fields around Baku that they so desperately needed to keep fighting the war.