The US Constitution is so sclerotic it still doesn't have an Equal Rights Amendment; were the Old Country to turn into a de facto* dictatorship it would probably be by other means than constitutional amendment. Look at Imperial Rome: they kept the form of the Republican legislative body, yet demonstrated its value by appointing actual horses to it...

* if needed, de jure soon after merely by retroactive application of new law; cf https://en.wikipedia.org/wiki/Night_of_the_Long_Knives#After... and Ultima Ratio Regum.