Yes, that’s how I would assess the matter. Historical counterfactuals can be a guessing game, but I find them fascinating if the issues discussed are plausible.
Without Hitler’s declaration of war I think the public anger and focus would have remained overwhelmingly upon defeating Japan, and it would have been a tricky issue over some period of time to get enough Americans to realize that direct US involvement in Europe and North Africa was essential as well. It probably would have come, but there would have been some period of time in which our main focus was on the Pacific..... whereas with Germany at war with the USA the official policy within the Pentagon was “Europe first” I believe.... although certainly huge major resources did go to the Pacific as well.
Official policy was a “Europe First” position. This was first set forth in Admiral Stark’s Dog Plan memo of November 1940. This position was affirmed in the ABC-1 Conferences which this Atlantic Conference meeting can be considered a portion of.
The reality was somewhat different though. By the end of 1942, despite the fact that we had invasion forces in North Africa, there were more troops committed to the fight against Japan then there were against Italy and Germany (460,000 against Japan vs 380,000 for Italy and Germany).
A good book on the subject of these agreements and how they worked in practice is “Allies and Adversaries: The Joints Chiefs of Staff, the Grand Alliance, and U.S. Strategy in World War II” by Mark A. Stoler.