How did the global balance of power change between 1900 and 1945?

It changed during World War 2 II. December 7, 1941, was a traumatic event in World history. The Japanese attacked the Americans at Pearl Harbor. Then Hitler declared war on the U. S. In 1945, the U. S. claims a world's primacy as the world's superpower by dropping two nuclear bombs on Japan and the Nuclear Age began.