Even spielbergs much acclaimed "historically accurate" saving private ryan is one sided (was there anyone else apart from the yanks involve??) and either inaccurate or plain wrong in some instances.
I thought everybody knew that the Yanks won the war and 'saved our asses'!
We, of course, were just sitting drinking cups of tea.
No hitler lost WW2 by opening up the eastern front. Yanks simply used the war as a cynical method of making money and breaking up the british empire.
Yes, the Americans did pretty well out of the war, at least economically, whilst Europe - both sides - finished the war a lot poorer than they started it.
I don't think the war accounts for our loss of empire, though. Like the Roman Empire, it had grown too big to last for ever. The Soviet 'empire' was the same. No empire has ever lasted indefinitely.