The causes and effects of WWII mostly focus on European issues, especially as it concerns Germany and Russia. Hitler's rise, brutality against other Europeans, and his eventual fall encompass the majority of the lessons we learn about WWII. Americans learn about the allies of Hitler, which includes Japan, but Japan is rarely the focus.
The causes of the second world war focus solely on the European Front. It is not often that people discuss the Pacific Front and the animosity and atrocities that the Japanese conducted against the Chinese. Despite this, the War did start in the European theater, and other countries simply joined.
World War II started in Europe in 1938. The Pacific Theatre didn't really start until 1941. The causes and effects of World War II started in Europe, so the focus of the world calamity should rightly be there. Without Adolf Hitler, Japan wouldn't have been so bold as to invade China and then attack Pearl Harbor. Without Benito Mussolini, Hitler wouldn't have tried to invade so many European countries.
I believe studies do tend to focus on the causes and effects of World War II in Europe rather than the Pacific. I feel it is this way especially in school studies for Americans especially at middle school and high school levels. I'm not sure why this is the case.
I do not think the studies of the cause and effect of the World War II was more focused on one side over the other. I think it outlays both sides equally and shows what happened than what resulted after wards. I do not think it makes one side look worse or better but just tells us the facts.