Forget the "after" part.
When you get right down to it, FDR recognized the looming danger and had been preparing the US for war for at least 18 months prior to the Pearl Harbor attack.
For that reason the US -- though still not prepared -- was already working hard to get prepared.
With Obama at the helm, we'd have had the tedious sermonizing and the feckless lack of action... and it would have been years before the US could achieve a full wartime capacity -- if ever. And because Lend-Lease would never have happened, Britain would have been overrun and the Germans would have won.