The TV series The Man in the High Castle depicts an alternate reality where the Axis won World War II.
In the show, a World Map is shown in some episodes, here is an example:
The red areas are the lands of the Greater Nazi Reich, the blue ones form the Japanese Empire, while the white/blank parts apparently are unclaimed lands.
At least in North America, we know that between the Greater Nazi Reich and the Japanese Pacific States this relatively narrow strip of land is a Neutral Zone.
In other parts of the World, these unclaimed lands are way bigger and extended.
Why are these lands unclaimed? The series is set in the Sixties, so if the two superpowers wanted, they had plenty of time after the end of WWII to conquer even these. Is is stated somewhere why such a great part of the world is left unclaimed?
This question is primarily focused on the TV Series, but I accept even answers from the novel. I read it, but many years ago, and I can't remember all the details.