I think you'd find reasonably strong support for the argument that the United States has a long history of poor adherence to its ideals of liberal democracy, including at least 86 years during which the ownership by persons of another human being was law of the land, a 500 year genocide against the original inhabitants of the land, armed suppression of populist, worker, and labour movements, imperial aggression and invasion of its multiple neighbours (Canada, Mexico, Cuba, Haiti, the Dominican Republic, Panama, Nicaragua, ...), numerous high-level political assassinations, a national political surveillance organisation run as a personal feifdom from 1924--1972, and with numerous internal fascist, militia, nationalist, and genocidal movements, amongst others, including an instance of a rogue President who ordered surveillance and burglary of political opposition in the 1970s.
There was a period of respite from that following Nixon's resignation in 1974, the Church and other hearings over FBI and CIA overreach, and the attainment of some of the goals of the Civil Rights and Peace movements of the 1950s--1970s.
None of that obviates the argument that there's not been a considerable backsliding and numerous unprecedented developments in the subsequent decades, including over the past administration and to the present.