I argue that Pax Britannica lingered on into the end of WWII , but as soft culturally-economic power, not hard military- economic power.
The British brand had a lot of strength against the America brand - it still had a lot of moral capital.
Not the least because Britain had stood all alone defending the world's Four Freedoms while isolationist America had yawned like a bored bystander watching a schoolyard bully beat up a pre-schooler.
Winston Churchill had led that fight but in the Fall of 1942 - unknown to most - his party, the Tories, had thrown away most of the global good will , all in an instant.