Good luck trying to get past the idea ingrained in the minds of all Americans from youth that the U.S.A won the war almost single-handedly like John Wayne riding into town with a couple six shooters, saving the frightened and defenseless women of Europe (U.K/U.S.S.R) from the evil hun. You tell someone that the vast majority of German military casualties were sustained on the Ostfront and most of the time you'll run into "but... but.. but...". Europeans know better, and of course the more well informed and read Americans do, but Joe Q Public thinks Patton won teh war.
True, it was a total effort, by all the allied nations...If you take 1 of them away, you can see what happens:
BRITAIN OUT: With Germany's Western front secure, they can bring ALL of their resources to bear on the USSR, Since the U.S. will play hell trying to strike at Germany from across the Atlantic, with no Staging areas in the British Isles.
USSR OUT: Just like the no UK scenario, only this time it's in reverse, This gives the german's a very good chance to invade england, once all of their manpower, material, and industry don't have to feed two fronts.
USA OUT: without American support, such as lend lease, Industrial Raw materials, equipment, etc. The Brits are in real trouble, both at home and abroad. The soviets, whilst not recieving quite as much aid from Lend-Lease as the UK did, Still needed everything we could send them. If Britain has no help, then this scenario might rapidly turn into the BRITAIN OUT scenario, only this time Russia has no help from the US, either.
Quint, whereas I agree that Most US schools are lacking, as far as history is concercerned, It can be said that a large part of the allied victory in the Second world war was due to US involvement on the side of the allies. What really crippled the Germans was'nt the Tactical air attacks on Wermacht units on the Russian front, but the RAF Bomber command and the U.S. 8th AF's bombing campaign against Industrial germany. If that campaign had never started, Hitler's war machine could have changed the tide of the war in the east, as well.
Edit:I do know that the USSR lost 20million+ during WWII...But, as has been previously stated, That was through alot of ineptness on both Stalin's part, and that of his General Staff(Those who had survived the purges of the '30's,) and also through German policies on how both prisoners and subjugated territories were treated.(the Gestapo rounded up Jews wherever they could.)