US and the USSR emerged as the two greatest powers for two reasons. Firstly, they had plenty of recourses and manpower, and the industry to use them. Both the US and the USSR had lots of factories, so they could turn their iron, coal, steel, and oil into goods. They could also use these resources to rebuild their Nations, although in the case of the US this was not necessary. This bring me to my second point, they were the only ones left. The British were bankrupt and London was in ruins, at the same time their colonies were diserting them, France was bankrupt as well, and was also losing its colonies. In addition France never had the industry or population of even Britian. Germany was being occupied, so that gets them out of the picture. China was in the middle of a civil war, and did not have very much industry. Japan was in ruins, and was occupied. I would add that despite its problems Japan was able to become a powerhouse. There are other reasons, but it would take to long to write
