Are you specifically talking about just who started the war? Or are you discussing the relative morality/'goodness' of each nation involved in World War II? The answer to the latter is every nation, axis and ally, engaged in morally dubious actions that resulted in the deaths of innocents for little apparent gain towards ending the war.
As for how the United States contributed to the start of World War II, it's two different stories. In the Pacific, Japan saw the United States and the ABCD powers (American, British, Chinese and Dutch) as competitors for the resources in the Pacific, and believed that those nations sought to stymie Japan's industrial and imperial growth. As evidence of this, the Washington Naval Treaties gave Japan 3 major warships for every 5 British and American ones. Moreover, Japan was highly dependent on imports from the ABCD powers. When President Roosevelt implemented a fuel embargo on Japan, it had the potential, and ultimately did, strangle the Imperial Japanese economy. In the Japanese view, the US made war inevitable when it decided to confront Japan over its imperial expansion.
As for the European theater, the United States held a lot of war debt from Britain and France, who in turn were entitled to reparations from Germany. This resulted in a system where German war reparations were used to finance British and French World War I debt, contributing to the conditions that allowed for the rise of Nazi Germany. In addition to the war debt, The Great Depression was a worldwide economic crisis that originated in the United States. Irresponsibility and ineffective response to the economic crisis turned the Great Depression from a shock to a catastrophe, which rippled throughout Europe and created the conditions for the rise of Facism.