Based on the popular book by Philp K. Dick, the Man in the High Castle takes place in a world where the Axis Powers won the Second World War and have divided the world between Germany and Japan.
As the old powers of the world fell, a new order arises to reign over what they've left behind - the whole world at their feet.
In both Europe and Africa, the bastions of liberty of France and Britain have fallen to the thunderous storms of Nazi Germany and their Italian allies in mere years, soon followed suit by a catastrophe in Eastern Europe, where the Soviet Union experienced an inevitable collapse. The Axis have firmly enforced their domineering authority over these two continents, and many of what used to be their enemies are now forced to kneel before them and their policies.
Out in the East, Japan has consolidated its own hold over the entirety of the Pacific and a large chunk of Asia - what remained have no chance to even make a difference. Fortunately for their subjects, the Japanese Empire is more virtuous compared to their European counterparts, and their people enjoy more rights than anywhere else under the Germans' thumb.
In America, the American superpower and any other states that had the potential of being a threat to either world power were simply annihilated; the United States have been divided into three nations, one for the Germans, one for the Japanese and a buffer state accurately named the Neutral Zone in the center. This could also be considered for the rest of the continent as well - many previously independent nations were split, forcefully puppeted and some even annexed.
Nevertheless, despite the new order's attempts at pacifying the world, people of occupied nations have staunchly rejected their authority and still carry on active resistance; though small in nature, with more support, they could easily top the short-lived new order.