I’m not sure WWII could have been completely avoided. It’s an interesting proposition because if we hadn’t given aid to the British or Chinese, it would have been interesting to see whether or not the Japanese would have seen us as a threat. I believe eventually Imperial Japan would have attacked us in some way, perhaps one of our military outposts in the Pacific or even the Philippines, which they did right around the same time as Pearl Harbor. But the administration certainly wasn’t trying to stay neutral.
Ultimately (assuming we never got involved) I think the Russians would have overwhelmed the Germans and the Chinese population would have been too much for the Japanese to handle. But it’s all hypothetical.
I think if we had taken a defensive posture instead of an interventionist one, we could have had a navy and air force second to none that could have warded off an invasion. We poured alot of resources into Europe before Pearl Harbor that could have gone into our own military buildup. I think a military buildup, along with non intervention would have been the best policy during the war in Europe. The obvious weak point for us if they did decide to attack would of course be Hawaii, along with the territories we acquired from the Spanish American War. That's kind of ironic, since we acquired all of those through our own imperialism. Just goes to show Empire is not sustainable. Which leads me to the reason why I think an attack on us would not have been a certainty as some have said. Empires have never been sustainable. Alexander the Great, Napoleon, the Caesars, all of them conquered huge areas, but in the end they lost it all because Empires are just too freaking big and costly to control effectively. You're right though, there's alot of hypotheticals, but it is interesting to ponder.