The most obvious change is that both nations' defeat and occupation by the Allies changed them from dictatorships to democracies. However, a more detailed answer is (at least IMHO) a question for a history book and would be far out of scope for a website such as this. There are hundreds of good histories of WW2 out there - check with the reference librarian at your local library for some suggestions.
japan
Douglas MacArthur .
WWII was fought all over the world which is how it gained it's name including North Africa, Eastern and Western Europe, The Pacific and several other countries. The highest point of fighting was done in Europe. {ADDITION}: The correct term for this is WWII. And this took place ALL over the world. The war leaders are Germany [Adolf Hitler], Italy [Benito Mussolini], and Japan [Haidiki Tojo].
Japan was always a militant country, Samurai Warriors & Feudal systems, much as the Knights in Europe were doing the middle ages. Modern conquests began in 1894 beginning with the Sino-Japanese War.
The political and social climate of the world in 1944 was one of upheaval and uncertainty. The outcome of World War II was still not known. It wasn't a given that the Allies would win and restore peace and democracy to most of Europe.
The United States proper was not damaged or seriously affected by the First or Second World Wars. America helped to rebuild Europe, Japan & the Philippines after the Second World War.
In Japan and Europe
Throughout Europe and Bombed in Japan
What areas outside of Europe were affected by the war
World War I changed the alliance system in Europe and had grave mental, economic, and political consequences for Germany that contributed to Hitler's rise to power.
They were nearly wiped out
Great Britain & the British Empire & Commonwealth. Russia and many other countries in Europe. WW2 affected most parts of the world.
Just Europe; in Asia they were fighting their own war.
hiroshima and nagasaki in japan
Japan received many of the former German colonies in the Pacific in exchange for its contributions to the war effort.
IN Europe and Japan fighting World War 2
japan america europe britain