This country was founded on the murder of natives and the exploitation of slaves/immigrants: that foundation has reverberated throughout our entire history. Government/corporate policy, often racist and sexist, works to maintain a permanent under class of exploited workers that provide cheap labor for the ruling class (e.g., sharecropping, Jim Crow, redlining, denial of reproductive rights, corporate offshoring, ever-increasing cost of living, etc.).
Not to mention the devastation that America has inflicted on the developing world. Obvious examples include millions of civilian casualties during our wars in Asia and the Middle East, foreign resource extraction that provides us with cheap consumer good (e.g., banana republics in South America, slave mines for metals in the Congo, etc.), and CIA operations that have been openly declassified (e.g., overthrowing presidents, installing dictators, disseminating propaganda) because this country can’t even pretend to live up to its professed ideals. Any serious study of American history suggests this country has never been “great” in anything beside our wasteful military expenditure and our inexhaustible favoritism of the wealthy. Trump is revealing how sick this country has always been and anyone who wants to go back to "normal" doesn't understand what brought us here.