This is was done by playing as Germany till late 1942 then switching to the US after invading NYC.
Feburary 26th, 1943
The world is in flames as the German Reich and its allies destroy any opposition. Germany has destroyed the USSR tearing it apart into puppet states run by her Generals while the Japanese take China and Siberia exploting every resource possible, The Italians control East Africa and parts of North Africa as the Free French and South African militaries start to exploit the Italians being unprepared for more war. In Western Europe a facist regime controls France while German puppets watch over Holland, The United Kingdom the Empire in which the Sun never sets has fallen, its goverment forced to flee to America while a goverment is set up in England by the Germans. The sun has finally set on the British Empire. The last major power in the world that can fight the Axis is the United States of America, however she is weak and with German forces holding most of her industrial centers it does not look good for the free world. Along side the USA stands Canada, Australia, New Zealand, the Dutch East Indies, and the British Raj. The Raj and the East Indies however are ready to fall to Facism without US support which is a long ways off with German forces constantly crashing against the Mississippi defensive line.
In the North of United States and parts of Canada US General George S Patton and his Third Army hold a defensive line stretching from Hudson bay to Grand Forks in Minnesota, His M26 Perishings and M4A3E8 Shermans battle against German Panthers and Tigers battering them but many continue on due to the rarity of HVAP rounds. Further south in St Louis General Douglas McArthur holds out against Field Marshall Heinz Guerdian while the US gold reserve is once again moved farther West. As a German bridge-layer finishing laying a bridge it is destroyed by an American 90mm AA gun modified for AT duty and blocking the bridge stopping German troops from crossing. In the air P-51 Mustangs and Gloster Meteors along side highly prototype F-84 Thunderstreaks battle against ME-262s and Ta-152s for dominace in the sky while P-47 Thunderbolts and Hs-129 ground attack planes strike armored columns and hardened defensive points.
In the only major Naval base east of the Panama Canal(Under German Control) what remains of the USN and the once British now Canadian Royal Navy recuperate after the disastrous battle of Panama Canal where over 120,000 US and Commonwealth sailors lost their lives. The USS Iowa as she sank fired off her last salvo which destroyed the German battleship Tirpitz before sinking beneath the waves. The USS Enterprise and HMS Invincible nearly escaped but due to battle damages both were scuttled and the crew brought home on the HMS King George V and USS North Carolina. The USN started the war with 9 carriers and now has none. With Germany in control of the waves the US and Canada are unable to help South African and Free French forces in Africa.
Although it looks bleak for the Allies there is still hope, in the Rocky Mountains of Colorado and New Mexico a team of scientist and engineers headed by Rober Oppenheimer work day and night to build an Atomic bomb before the Germans. They already have succeded in building a nuclear reactor which has been put to use producing the fuel for an Atomic bomb, however this is not the only use for nuclear energy, in San Francisco the newly built shipyards have started work on a new type of Aircraft Carrier. The ships are powered by nuclear power instead of the normal steam turbines, the lead ship of the class named for the last USN carrier to sink is the USS Enterprise. Along side the Enterprise-class CVNs come the Montana-class Nuclear Battleships both ships still have a long time ahead of them before being ready to fight the Kriegsmarine. (Note: No idea why but when I switched to US they already had CVNs and Nuclear BBs locked ready to research despite it only being late 42 but I'm not complaining. Seems like the Ai glitched out and since 1933 has been rushing carriers all the way to CVNs same for BBs)
