Japan only decided to act against the West following the American embargo, most crucially of petroluem and related products. There's an implicit assumption that something similar would have to occur for Japan to embark on a similar course.
Umm... The oil embargo was only after Japan had started to take over French Indochina. They had no need to do THAT unless they were already planning to head south. So, I don't believe your statement is correct at all.