What changed politically in countries from different parts of the world from before to after WWII?
The major change from before to after WWII was that some countries became more democratic while others became more totalitarian. This broke down roughly along the lines of the two blocs in the Cold War.
Before the war, countries like Japan, Italy, and Germany had authoritarian and fascist governments. After WWII, they (with the exception of East Germany) became democratic. By contrast, some countries became less democratic than they had been. This was true of such countries as Czechoslovakia and Poland which had been relatively democratic but which ended up behind the "Iron Curtain."