The United States of America was a thriving nation with a stable government. After President Franklin Delano Roosevelt was assassinated in 1933, the country was never the same as before. When the Crash of Wall Street had begun, their current government was not able to recover, resulting in them not being able to support the Allies during World War 2. After the collapse of the Soviet Union, Nazi Germany and Japan launched a frontal assault on both sides of the US. Nazi Germany dropped the Heisenberg Device on Washington D.C. 11 December 1945, resulting in the collapse of the United States Government and the senior military leadership. Although the government had collapsed, its citizens fought hard to prevent an Axis takeover of the country. The Resistance fought a hard and tenacious war against the Axis Powers for almost 2 years, until they succumbed to the Axis Powers. On 18 September 1947, Victory over America, and their surrender had been achieved. In 1952, Adolf Hitler had announced that the Axis Powers had eliminated all members of the Resistance and that America has fallen and been conquered. Ever since the war, there has been bitter and anger feelings between the Axis Powers and the former United States residents.
We get the first official glimpse (outside of the films) at an alternate history when Tagomi appears to have "jumped" via meditation to an alternate" 1962 where the United States and the Allies won World War II. The country was never invaded and divided. In this alternate 1962, the United States is engaged in a Cold War with its former war ally, the Soviet Union, and both countries were close to armed hostilities due to their involvement in the Cuban Missile Crisis.
Unlike in Nazi America, the capital of the United States in this is still located in Washington D.C. and the President of the United States is John F. Kennedy (as evident on the front page of a newspaper Tagomi saw on a bench in San Francisco's Union Square). The flag of the United States in this "alternate" 1962 has 50 stars in the blue field (denoting that Alaska and Hawaii were made official states of the USA).