“Churchill (the UK) was not alone. Russia was doing the fighting and dying to bring down the Nazis on the Eastern Front. Maybe you didn’t learn this in your history classes? Here’s a refresher for you:”
The Battle of Britain occured before the Soviet Union was invaded. Here is part of the speech that should make clear to you what time frame Churchill was talking about:
“After a while we were left all alone against the most tremendous military power that has been seen. We were all alone for a whole year.”
From the fall of France in late June 1940 till the German invasion of the Soviet Union in late June 1941 and America’s entry in the war in December 1941, it was the British Empire and Commonwealth that was fighting Nazi Germany.

And while Britain stood alone, the Soviet Union was Nazi Germany's biggest trading partner.
Your word-choice completely masks the fact that the Soviet Union and Nazi Germany were "best buddies" before Hitler decided to stab Stalin in the back.
The Soviet Union and Nazi Germany joined forces to carve up Poland amongst themselves, as per the Secret Protocol of the Molotov–Ribbentrop Pact.
Regards,