Historian Campbell Craig argues that FDR's decision to take America into WW2 was controversial at the time and that some historians, like Charles Austin Beard, believed it to be a conspiracy. However, FDR may have had a more far-seeing perspective on the situation than the American public, which later approved of his decision and discredited Beard's argument.
Modern histories on WWII offer an opposing viewpoint that the war in China was a proxy war not only for the US but for Great Britain as well. Japan was already in a war with the US, as well as the Soviet Union, without a single US troop, and FDR was possibly following that principle.