In bluntest terms, the entire debate is one which I find fairly groan-worthy as it suffers from several intertwined issues. The first is that it usually attempts to make certain factors vastly more important than others (for instance focusing on lives lost as the ultimate marker); the second is that is generally looks to downplay ones which don't work in favor (such as the degree of criticality of Lend-Lease); and third it inherently is an argument which avoids engaging with how interconnected all of it is. I have a few previous things written which touch on some aspects of this which I'll link with some slight additional commentary.

Take for instance the importance in Allied bombing raids conducted during the war. There has been long running debates about just how effective strategic bombing was, but was was absolutely true was its importance in forcing the Germans to concentrate large amounts of aircraft to defend against them which in turn relieved pressure on the Soviets and was critical in allowing them to gain the upperhand in the air war on the Eastern Front in the latter part of the war. And likewise in the linked post, Lend-Lease gets handwaved away without any serious engagement. Never mind the absolutely critical factor it played in the USSR as a military force, but one often under-appreciated aspect is the amount of food aid, which likely was the difference between widespread famine in the Soviet Union. Both these aspects are touched on here and here.

One final thing worth harping on is that these debates, if we can call them that, as they play out online, generally don't engage in serious thought experiments of the counter factual, that is to say, actually putting serious thoughts to what would happen without the United States, or with a significant change in what the US was contributing. Aside from taking it as a given that the USSR would do just fine, which we absolutely cannot, any meaningful presentation also needs to consider why the US wouldn't have been contributing in the same way or why we can justify devaluing any specific contribution, whether it be the US, the UK, or the USSR, when trying to build up the importance of the others. As I sketch out here, even relatively minor changes likely would have big consequences., which ties back to the main point, namely that of interconnectedness. To be sure, there is a certain style of American braggadocio which implies the US won WWII, by itself, with one arm tied behind its back, and it is an argument which ought to make anyone groan, but the overcorrection that people then offer to try and say the US was ultimately not much of a help is simply just as bad.

If there are any specifics you might want expanded on beyond the general sketch above, do let me know but you'll have to wait until tomorrow!