John,
No one doubts the Russians put in the biggest amount of work in Europe...but...WWII was also fought in the Pacific against Japan, which Russia didnt really participate in till the very, very, end...
so, I’ll give you the Russian 70% against Germany...we had about 90% of the War against Japan...net, net, the US made the greatest contribution to winning WWII...though Russia sacrificed the most lives.
You need to read Norman Davies’ account.