Americans by and large were not at the center of the decision to enter World War II - until Pearl Harbor. There's at least some evidence to suggest that the top levels of government/military let Pearl Harbor happen. And if we choose to not go that route, there are the large corporate interests at stake. Looking at the US presidential elections of 1940 - there were no candidates on the Republican side that would not have found a way to get us involved in WW2, openly or covertly. I'm cynical in these respects, obviously...
Deterring America from participating (though we were helping England directly and I think Germany indirectly, if just on a corporate sharing level) would at the very least involve no Japanese action at Pearl Harbor or the Philippines, and Japan avoiding serious provocation of England. U-boat attacks in the Atlantic would need to be reigned in, and likely there would not have been an Afrika Korps. A major propaganda campaign in 1940 letting England know that Germany's interest was retaliation against France for its 1923 incursion would have been needed.
It would have taken an active effort by the Axis leadership in both theaters to convince England (and the US by extension) that it had no real issue with them. I'm not sure that would have worked either, but add a few corporate deals, tech swaps, and oil deals, very early on to cement a relationship. Either way, we do have Hess flying to England in 1941 before Barbarossa and the details of that have never been released, the circumstances of his "suicide" in prison as an old man "suspicious", and all that - who knows.