I'm sure you know this, but "WWII" is not a verb. The United States did not decide "to WWII" instead of "not WWIIing".
Japan aggressively invaded neighboring countries for resources and engaged in ethnic cleansing. The United States imposed a gradually more strict embargo of military and dual-use materials, including eventually oil. This precipitated the Japanese invasion of the oil rich Dutch East Indies and the attack on Pearl Harbor to cover for it.
If the question is "What should Japan have done?" the answer is "Not try to conquer Asia and not attack Pearl Harbor." If the question is "What should the United States have done?" the answer is not "Not try to conquer Asia and not attack Pearl Harbor." The answer might be "Disband the Pacific Fleet," or "Pay Japan not to invade its neighbors," or "Ally with Japan against Britain," or "Preemptively invade Japan," etc., but if you're trying to direct Japanese fleet movements or German concentration camp policy or the like, you're not engaged in an exercise showing the United States should have done anything differently.
Noah Millman wrote:
Link (which includes additional good retrospectives) thanks to Ampersand.
This article may have more political content than is suitable for LW-- if you'd rather discuss it elsewhere, I've linked it at my blog. I've posted about it here because it's an excellent example of updating and of recognizing motivated cognition even if well after the fact.