There is the US not-an-Empire [0] though, that'll probably count when the history books reflect on the present era. WWI/II can very easily be interpreted as a transition of power away from incompetent British leadership (indeed, European monarchies - the change pre- post- WWI is striking) towards more capable US-based leadership.

It isn't clear UK public ever really grappled how insufficient their leadership theory is. Their acceptance of poor performers over the last 20+ years has been striking although it is mirrored by low standards in the US.

[0] https://en.wikipedia.org/wiki/List_of_American_military_inst...