How about this. Pre WW1 germany makes an alliance with britain. When the fighting starts, germany & austria hungary vs. france and russia, and serbia britain joins in with germany.
Germany also sends zimmerman telegram to mexico, and makes an alliance with them. The US eventually find out about this and along with submarine warfare, it makes them declare on germany and great britain. Trench warfare starts on all of the US borders in north america, and the US navy is beaten by the royal fleet.
By 1917 the consists of Italy, turkey, britain, germany, austria-hungary, mexico and japan on one side, and france, belgium, russia, serbia and the US on the other side. The war ends in 1920 with germany victorious.
Germany, austria, bulgaria, the ottamans, and italy form an economic union, and force the defeated french, belgians, and serbians to join. Soon afterwords the netherlands, denmark romania, norway and sweden are pressured into joining along with the newly independant nations carved out of russia: poland, finland, lithuania, latvia, estonia, belarus, ukraine, moldova, georgia, armenia and azerbaijan. Germany and britain split the french colonial empire.
The united states was economically ruined by the war because every border was a battle ground and the combined german and british navies were blockading their ports. Britain takes alaska, hawaii, the phillipines and puerto rico from the US.
Russia was in ruins at the end of the war, but germany propped up the czars against the revolution, in exchange for resources and an alliance.
With britain and germany dominant in the post war world they begin a struggle similar to the cold war, with the british empire against the german economic union.
The united states struggles with economic hardship after the war and a far right wing party comes to power in the mid thirties. They advocate US expansion and for the united states to replace germany and britain as the dominant world power.
Over time germany grew more and more democratic, so that by the late thirties the kaiser was just a figurehead.
Germany and britain eventually go to war in 1939 after a series of border conflicts between german namibia and british south africa. The war is a stalemate at first, because the boarders between each side are far from the central nation and each country fears attack on the homeland if they shift troops to the border. This goes on until 1941 when facsist america declares war on britain and invades canada. This tips the balance in favor of germany because britain to shift troops from elsewhere to defend canada. germany and the US gain ground until 1944 when the german government recieves a message from britain asking for an alliance against the US, which has conquered all of the territory north of it's border, as well as the british possesions in the caribean.
Germany wavers, but when britain show them evidence of US atrocities in the war germany agrees. The treaty is very in favor of germany, making britain a member of the german economic union, and giving germany many colonial gains. From 1944 to 1950 The US desperatley fights against the vastly superior forces of germany, britain, and all of their allies. On august 12, 1950, germany drops the atomic bomb on New York the City, threatening more destruction if the US does not give up.
The US surrenders, giving back all territory it took in the war, and being forced to allow german occupiers in the country. Most of the US has by this time been devestated by massive bombing raids, and it is reeling from the huge losses it suffered during the war.
Germany is now the sole superpower, with britain and the US defeated, and much of the world either directly controlled by it or in an alliance. Germany is very prosperous, and builds up a space program in order to show its superiority.
