I believe history reveals that the consensus in the US was for non-involvement in the war in Europe. . The Government was aware of what was coming and had to ramp up military production. Under Roosevelt there was the Lend Lease act to supply weaponry to England, Russia and China. During the three term President the Allies defeated the Axis powers. I don't recall what percentage of politicians Democrat or Republican thought going to war was a good idea in the 1930's.
I wouldn't overlook the comment based on first hand experience of my Army neighbor. If the people you are fighting for aren't in the fight how can there be an ultimate victory.
Anyone remember the Vietnam War? The French were defeated and the US got involved using the "Gulf of Tonkin Resolution " to escalate in a manner that sped up our involvement. The "Domino Theory" fanned the need to square off against the China, Russia backed North Vietnamese. Now, fifty years later we trade with all three of our sworn enemies. Would an earlier and more costly involvement in Vietnam changed the outcome and at what cost.
It is difficult to speculate about the earliest moment to engage in mankind's most destructive achievement to bring about the desired result. The cost in human life is not a petty thing.