Re: USA probably at the root of it
Even today the British economy is three times the size of Russia's, and while the rest of their empire was more developed (even after much of it was looted and flattened twice) that also meant maintaining control was harder, and the rest of our empire was huge and under-utilised.
The habit of surrendering to colonial rebels as soon as they were defeated didn't help, but that had been the basis of Britain's "imperial" policy for half a century already and was the main reason it was in decline. Joining in American foreign policy decisions without thinking, and getting into pointless wars as a result, only made things worse. Its especially a pity that no one told Wilson to shut up and carried on the WWI peace negotiations until winter 1919, when Germany would have capitulated and could have been carved up and abolished.
(Also, if we'd had an adequate supply WMDs that would have cut the imperial security cost enormously, because the garrisons and security forces could be removed, with the district officers protected by the threat of massive retaliation against their territories if anything happened to them.)
Biting the hand that feeds IT
