I submit to the Board:
America moved to cripple Japan's wartime economy in September of 1940, prompting Japan to try for one great throw of the dice. Could America's embargo in response to Japanese expansionism be moved up to the period between the invasion of Manchuria (81 years ago today) and the assault on China proper (on 7/7/1937)?
The Chinese are still extremely angry about this, by the way.
On reflection the above sentence is an enormous understatement.
So where to start? To my mind you would need at least two ATL figures. A very public string of Japanese atrocities must make front pages in the US, which would demand a famous American journalist sneaking around, probably actual American deaths, and perhaps even worse behavior from the Japanese than OTL. Even then, I'd guess - not knowing the details - that someone would have to be thinking very differently in the Roosevelt administration. Congressional support might well be required, which would make the entire enterprise even more difficult.
So what say you? Could it be done? How?
And of course, what effects would this have? Would the Japanese be as able to digest Manchuria with essential economic and war materiel drastically lacking? Would they even get the chance with China more than happy to fight on now there's some chance of winning? Would Japan attack America early, and risk the wrath of unoccupied Europe?