I agree that the USA certainly helped minimise British and allied losses and that it speeded up the victory over the NAZIs. I just get irritated when Americans try to take the whole credit for the allied victories in WWI and WWII. If I remember correctly Hitler himself said that if the war ended quickly Germany would win, but if it dragged on then it would probably loose. The USA's lend-lease agreement which supplied $11 billion to the USSR was very important to the allied war effort, since it helped to sustain the ailing Red Army. I wonder if the Soviets ever paid the USA back?
I believe that even if the USA hadn't joined the war in Europe and had just continued to support the allies with economic aid and arms shipments, then Hitler would still have been beaten, but at a much greater cost in allied lives and resources. But, of course, most of continental Europe would have ended up under the boot of the Soviets. Hence it was in the USA's best interests to get in and help Britain retake as much of Western Europe as possible.
Also note that Russia and Germany were allies and divided Poland. Hitler then turned on Stalin. Without US and British help to Russia and the threat of a second front with the US and Britain, Hitler could have fought at least to a standstill - until he had the atomic bomb.
Yes, I am well aware of the non-agression pact Stalin signed with Hitler and the fact that they divided up poor Poland between them. The Soviets were the scum of the Earth, they claimed to be the idealogical enemies of the NAZIs but collaborated with them to gain territory and power. If only we had kicked Hitler out of power when he first violated the treaty of Versailles.
I very much doubt Hitler would ever have got the atomic bomb. Werner Heisenberg deliberately stalled the NAZI atomic bomb effort and most of Europe's best nuclear phyicsists fled continental Europe because they were Jewish. Hitler really shot himself in the foot with his anti-Semitic policies when it came to scientific research. Have you read Thomas Powers' book: 'Heisenberg's war - The secret history of the German Bomb'.
But, without Churchill and the British fight, it would have been a lost cause for all of us. I vote for Churchill as the man of the century!
That's my point, it was a team effort. If Lord Halifax and that arch traitor Edward the VIII had succeeded in turning Britain into a NAZI client state we would all be speaking German!