It’s not just economics. Manpower and the national resolve are also critical. If the Soviets lost the Axis would have alot more manpower than our ability to match along with England, which was near the breaking point after many years of war. Thats why Churchill got replaced before the war even ended. The axis exploit its manpower much more efficiently than Western Democracies.
If the Soviets lost and UK was stripped of her colonies, its likely that USA would just be fighting Japan because of the direct threat, but our material advantage is unquestioned, the question is how many lives get lost fighting what becomes a lost war to save Europe with no prospect of hope…. the hope was coming from Soviets eating 85% of the total German military economy and with that removed, a huge problem of how many American lives will pay for Europe?
To me the public would not allow FDR to fight the Germans, but only support the japanese fight. Americans would not be willing to lose 8 million more soldiers just to save france and get back the Russian and British partners.
If you look purely at economics the axis in total were just a tad bit ahead of USA, but that does not count what would be coming in from occupied UK, lost British colonies, and a fallen Soviet Empire. For that i would add in new ratio of 1.4/1 in favor of axis.