What if WW2 had not ended until 1955?
Um, I'm having a hard time coming up with a scenario where the war that was very over in 1945 lasted another decade, but I'll try.
- Germany simply cannot formally surrender and the allies can't get a government in place so while the war is won, it still continues on paper.
- Germany manages to knock Russia out of the war and are getting supplies and force the Soviets to produce war time materials. With this the Atlantic wall would be better defended and better supplied making D-day less likely to succeed, but I doubt that's enough to help out the Germans so they need another advantage. The Wermatch employs many successful spies into the allied army and know most every move the allies will make allowing them to take away any elements of surprise and allow them to surprise the allies themselves. These are both possible, but unlikely. This would lead to the Germans capable of keeping the allies off the continent prolonging the war until a peace treaty is made in favor of the Germans.
- America votes to be completely neutral and supply any side that has the money to pay taking away a massive amount of resources from the allies and allowing the Nazis to get their hands on some resources. So Britain is forced to surrender and a long war is fought between the Germans and the Soviets. I can't really say who'd win because both would have to plan for an extra decade of war. All I can say is Germany has better odds this time.
- America Joins Germany and the Soviet Union holds out for a stupid amount of time which it can do.
Actually, it didn't end until after that - specifically, Japan and the USSR were still technically at war until 1956, when they agreed to a "joint declaration" ending the state of war. There has never been a full-scale peace treaty between the two countries (which would now be Japan and Russia), because they can't agree on who should own the Kurile Islands north of Hokkaido. Russia has occupied them since the end of the war.