How did the US save the day in the Battle of Britain?
I am not diminishing what the Brits did, it was monumental. When the main battle wound down in late 1940 Germany was still bombing England into 1941. Hitler’s mistake was after the Brits made an attack on Berlin, he ordered Goering to start targeting cities. Up until that point the German’s were making headway destroying Britain’s military infrastructure, so it was just a matter of time before Britain could have capitulated (we will never know because the battle plan changed).
The 2 events that eventually saved Britain was Hitler’s turn toward Russia in preparation for the invasion in June 1941 and then the Japanese handed Britain a bigger gift on December 7th.