The fallen "kings" are ex-presidents still alive.
Carter just turned 96. These guys aren't going to live forever. We are still a "fallen king" short.
I believe that Joe Biden will suffer at the hand of the Curse of Tippecanoe and will not leave office alive. To make matters worse, I also think that he will be assassinated by a disgruntled Trump supporter. Since there are no other "kings" mentioned in scripture it's safe to assume that Joe Biden will be the last President because his assassination sparks the next American Civil War which will destroy the country.