If we assume that 'America provided the equipment', then the first problem that arises if the UK capitulates in 1940 is that America cannot provide the equipment. By far the greatest bulk of American and British lend-lease aid to the Soviet Union was transported via the Arctic Convoys, which ran from Scotland to Murmansk. Roughly 7% of shipping in these convoys was lost, largely to U-Boat attack and air attack from German-occupied Norway, in response to which convoys were usually supported for at least part of their journey by allied air support. By 1944, 27% of lend-lease was transported via the 'Persian Corridor'. Both of these avenues are impossible if Britain capitulates in 1940.

With German forces occupying the UK, the Kriegsmarine would have unfettered access to the North Atlantic, and be able to establish air superiority out to sea, which would severely inhibit the ability of American convoys to even cross the Atlantic successfully let alone then continue from a now-hostile Scotland to the USSR. Without British forces in North Africa, Italian/German supremacy of the Mediterranean would also have rendered the 'Persian Corridor' moot as well as providing Germany with access to the Suez Canal.