I think adding that many more people, ships, and weapons has to make a difference. oOne thought that occurred to me is that ITTL the invasions of Normandy and Southern France could have happened on the same day. tThat would increase the pessism in the German military. tTherefore there is a more effective effort to kill Hitler. fFollowing Hitler's death there is a power struggle that weakens the German war effort.
Its an interesting idea but all those people need to eat, all those weapons need ammo, all those ships need oil and all the planes and tanks need fuel. And as far as the Ground War goes, just like IOTL there will be a severe supply bottleneck. IOTL the Germans held on to or wrecked every port in Western Europe so that until the start of 1945 every little bit of supply in the Western Front had to be driven from the beaches of Normandy to the front. (Ever heard of the Red Ball Express?)
Even with extra troops, the Germans can still do that, they have to do it, as its the only strategy they can use.
And doing that means that there is no point where the Western Allies can simply push forward like the Red Army can. The struggle for supplies would be made even worse, slowing things down even more.
Its easy to say that wars are won simply by the number of rifles or bayonets on a fireing line but its not, Logistics win wars, and your situation just makes that worse. There's just no way the Allies are going to be able to push much faster just because they have more men in theater.