As in the First World War, the United Kingdom (UK) would have to turn to the United States of America (USA) for supplies on the scale necessary for a large army. […] Overseas finance in the Second World War came to depend on the willingness and ability of the U.S. government to persuade Congress that it was in America’s interests that the British war effort should be sustained. […] However, with first lend–lease and then the USA’s entry into the war the British Army became increasingly reliant on American‐supplied equipment: for example, from 1942 more than half of the British Army’s new tanks came from the USA.^43^

(Source.)

Of course, Wall Street was ground zero for the Great Depression, which arguably makes Imperial America’s important contributions to the European Allies less impressive: solving a problem that you started is the responsible thing to do, but it should be baseline and rarely laudatory.

While we can still give some credit to the Western Allies for defeating the Axis, few historians disagree that the Soviets contributed the most to vanquishing the Third Reich. Even Winston Churchill, as much as I loathe him, conceded that the Soviets ‘t[ore] the guts out of the’ Wehrmacht.

Now this is typically when antisocialists refer to the Lend–Lease Act, whose importance they exaggerate to comedic extremes. While the Lend–Lease Act was undoubtedly helpful to the Soviets, we really have no good reason to believe that it was decisive to the Allied war effort:

From 1941 to 1945, total lend–lease aid to the Soviet Union accounted for only 5% of the Soviet GDP in total. And it is a salient point that over 80% of the aid was received after June 1942, when the tide of the war had already turned against the [anticommunists] on the Eastern Front. The Soviets had already won the critical battles of Moscow, Stalingrad, and Kursk. [Fascism] was already losing the war when Lend–Lease to the Soviet Union had any significant effect, and that effect was minuscule compared with Soviet production at the time. By the time the first Sherman laid its tracks on Soviet soil, the writing was already very much on the wall for the Third Reich.

Although Stalin, Khrushchev, and other Soviet politicians were very complimentary about the Lend–Lease program helping them win the war, the statistics tell a very different story. The noted historian David M. Glantz points out in this regard,

“Lend–Lease aid did not arrive in sufficient quantities to make the difference between defeat and victory in 1941–1942; that achievement must be attributed solely to the Soviet people and to the iron nerve of Stalin, Zhukov, Shaposhnikov, Vasilevsky, and their subordinates…”

He further states that without Lend–Lease, the Soviets still would have won, but the war would have taken 12 to 18 months longer.

(Source.)