Nicholas Kristof wrote an interesting comparison of the Roman Emperor Caligula and the American President Donald Trump. See "There was once a great nation with an unstable leader", Nicholas Kristof, New York Times, 2017-08-26.
See the comments for ideas on how much this is true and how much the current U.S. is more resilient.
For more on Caligula, see https://en.m.wikipedia.org/wiki/Caligula.
