I generally agree that Americans tend to downplay the impact of Russia in WW2 but there is zero chance Russia would have won the war without the US. Even Lend-Lease going away would have resulted in a loss. Both Stalin and Kruschev agreed there.

The British Commonwealth was the biggest factor in Africa, but it's questionable how quickly they could have won out and taken the Suez without the Americans coming in late in 42, which was critical for both vital supplies like oil and also invading Italy. Japan was already getting bogged down with China and even Burma so they wouldn't have suddenly been free to do much in the European theater but just getting Italy out of the fight and forcing Germany to replace their divisions elsewhere. Italy exiting the war removed 30+ divisions between the Balkans and France, while another 70 Axis divisions were being held down by Allied forces in the Mediterranean during D-Day, with there being 33 Axis divisions in Normandy for D-Day itself. A lack of US involvement also likely means that Germany is able to hold Caucasus for longer (and take more of the oil fields), solving a sizable portion of their oil shortage issues.

With Lend-Lease but no active participation in the war from a military deployment standpoint, the UK and USSR do likely eventually win but at much greater cost and not without risk of losing. Without Lend-Lease it is highly possible that the Axis wins, at least in the European theater. Japan had kind of set themselves up to lose from the start no matter what the US did.