In The Man in the High Castle, Nazi Germany controls the eastern United States.
The novel takes place in an alternate history in which the Axis powers won the Second World War. Germany occupies and administers the eastern part of the former United States, while Imperial Japan controls the Pacific States and much of the western region. The Rocky Mountain States form a comparatively independent buffer area.
This division creates competing political systems and cultures across North America. German rule is associated with aggressive expansion, racial ideology, and advanced technology, while Japanese rule is presented through a different imperial bureaucracy and cultural influence.
The book’s title refers to Hawthorne Abendsen, the author of a banned novel imagining an alternative world in which the Allies won. That fictional book is not the same as Dick’s own novel, although it drives much of the story’s intellectual tension.