They sure did, we didn't fight it for years before that and technically win it at the Battle Of Britain.
Please do not start a debate that you are obiviously ignorant about.
Read any non American history book concerning the facts about the war2 before you start spouting off.
It was a combined effort , but could not have been won without American entry and military supplies.
Please explain how there were as many American battle deaths in the European theater during their 3 yrs active involvement as total British battle deaths during their 6 year fight.
And the Russians lost more soldiers in WW2 ( over 10 million) than all of the rest of the European combatants combined. And that does not include the 13 million Civilians killed by german regular infantry in Eastern Russia.
The Air Battle over Britain was a heroic effort, greatly aided by the use of radar, and the spirit of the civilian population, But Hitler never had the naval equipment for an invasion and wanted to isolate England while attacking Russia. He may have succeeded in his attempt there if the Italians weren't so incompetant.
Anyway , everyone has bragging rights for the defeat of Hitler in WW2, but don't start knocking down American contributions to that war effort or its efforts since..