If I take your question to mean "saved Europe from the Nazis" then...

..The war in Europe last for 69 months. The USA was not an active belligerent for the first 27 of those months and the first meaningful American deployment against the Germans came with Operation Torch in November 1942, by which time the war was already 39 months old.

By this time, the Afrika Korps had suffered an irreversible defeat at Alamein and only days later the Soviets would launch Operation Uranus, trapping the 6th Army at Stalingrad. At this point the war was effectively unwinnable for the Germans.

In Italy, the US and British Empire deployed roughly 6 Divisions each.

For D-Day and the immediate period thereafter, the Americans deployed 19 Divisions while the British deployed approximately 14 Divisions, the Canadians 3 Divisions and the Polish and Free French, a Division each, and the majority of the air and naval forces being provided by the British Empire.

Against this must be weighed the fact that the Germans had been maintaining about 180 Divisions on the Eastern Front, with the Red Army inflicting 80% of all German casualties.

Thus the Americans did not even make up the majority of the Western Allies until the last 10 months or so of the war in the European Theatre of Operations.

Now, its not of course to say that the American contribution in terms of boots on the ground was insignificant, nor to deny that American industrial output was arguably a decisive factor in the final victory.

But to say that the Americans "saved Europe" is not a sound argument.