I know there are a few history buffs here on E, and I absolutely love to theorize this stuff! This is where we try and come up with as accurate a vision as possible of the world today if a great event had gone differently. You can jump in any time with a new 'what if', but I'm going to start with the simplest one first.
The war in Europe ended with the capture of Berlin by Soviet and Polish troops and the subsequent German unconditional surrender on 8 May 1945. The Japanese Navy was defeated by the United States, and invasion of the Japanese Archipelago ("Home Islands") became imminent. The war in Asia ended on 15 August 1945 when Japan agreed to surrender.
This didn't happen. Berlin held, the Japanese Navy held, and their counter attack won the war. Hitler set foot in New York shortly after. Germany has won. Fast forward to 2011. What could the world look like?