The bulk of American aid had not arrived until about 1943.
This is true. US support wasn't fully ramped up until early '43. The Soviets did receive assistance prior to 1943, though. You can find all sorts of photos of burning US and British made tanks that were taken in 1942. They also received quite a few aircraft early on; before the Soviet aircraft industry came into its own. US made trucks made up a bulk of the Soviets transport force through out the entire war.
The Soviets were within a hairs breadth of defeat in 1941 and then again in 1942; although to nearly as close as 1941. Every little bit helped them.