Anybody who pretends that the US hasn’t operated as an empire, there is even a book named “How To Hide An Empire” on it.
That insight ( the link ) of Glubb’s was important.
Please glance at the history backing it, in that table, on that page…
I believe it is partly that the empire-rulers identity becomes sooo completely mis-matched from the actual composition of the empire, that it is an inevitable self-destruction, at that age of its evolution.