> British empire was a rapid collapse [...] It collapsed within 20

It would be better to treat the British Empire and the United States as two forms of the same empire, as they both speak the same language The capital of the empire simply moved from London to Washington via an internal revolution, a process that's happened many times in the past, e.g. Lisbon to Rio de Janeiro, St Petersburg to Moscow, Xian to Hangzhou, Kyoto to Tokyo. So the British Empire/United States reached a peak after 400 years, and is now declining for perhaps a few hundred.