I think it was Shinto but I'm not quite sure.
"I think it was Shinto but I'm not quite sure." So wrote the previous poster. You think? You're not sure? Why did you even bother to answer?
The answer is too complex for a one-liner, but the religion of Japan was and still is predominantly Shinto. There was a State Shinto in place during World War II, but Japan was not a theocracy - indeed, it had separation of church and state written into its constitution. State Shinto was a politicized Shinto, used to underpin and justify Japan's nationalism and attitudes of racial superiority.
So the answer to the question is not clear cut. Shinto was not to Japan as Islam is to, say, Saudi Arabia today. Still Shinto was adapted and selectively interpreted by the state to support the militarist government's agendas and to manipulate and control public opinion. If you want a real understanding, you need to do some deeper research. It will be worth it. You ask a good question and deserve a better answer.
Japan
underwent political reform and economic expansion.
during WW2, there was no trade between Japan and the US
No. For centuries before and during ww2 Japan had always been imperialists.
22
Shinto is/was the official language of Japan.
December 1941.
It is the native religion of Japan and was once its state religion.
There is no "one world religion." There are many different cultures throughout the world and many different religions. Some nations have an official religion for their country, but there isn't a "one world religion" of any kind. Christianity is the most commonly practiced religion in the world, but it certainly isn't the ONLY religion of the world, neither is it the official religion of the world.
The world religion with the largest proportion of followers among the populations of both Japan and China is Buddhism.
The Soviets discouraged religion altogether, but there was probably a lot of Russian Orthodox sentiment still lingering out of official eyes.
Shinto religion is practiced in Japan.
The place of origin for Shinto vis Japan. It is Japan's national religion.
Austria-Hungary had no official religion, although the dominant religion was Roman Catholicism.
As far as I know, unless Japan has territories and colonies in other parts of the world that I don't know about, only Japan does.
Americans have changed Japan by not giving japan the proper exports during World War II.
Hideki Tojo was the dictator of Japan during WWII.