I don't want to idealize FDR as some kind of paragon of virtue. He was a good man for his time. America has always been a battleground between the forces of light and the forces of darkness. It's easy to make America look good by emphasizing the good works of those who tried to change America for the better while hiding the bad stuff (lynch mobs, Jim Crow) under the rug. Nobody gets a fully balanced picture and any imbalance is always heavily weighted towards the Shining City on a Hill side of the scale.
America has supported fascist dictatorships in Latin America, especially since the Bolshevik Revolution, when they were seen as the most reliable and strongest bulwark against communism. America has always paid lip service, however, to human rights and democracy, in Latin America and around the world. I think today their thinking has evolved to the point of probably preferring a stable, prosperous, right-of-centre "democracy," so long as the leaders of the major political parties are pro-American, pro-business and don't make waves. But in a pinch, they'll turn to the Pinochets and their ilk in any unstable situation.
I think overall the negative changes since FDR were in international rather than domestic relations. The racial issue has been slowly improving since FDR's time. Eleanor Roosevelt can take a lot of the early credit for that, but other Democrats followed in her wake, including Hubert Humphrey and LBJ and ultimately the blacks achieved a kind of very belated de jure equality, if not a de facto one.
In the international arena, things went from bad to worse. Even in FDR's time, he allowed the British to take sides in the Greek Civil War as early as 1944, leading to the defeat of the Communist guerrillas, who almost certainly represented the will of the Greek people, and the triumph of Royalist guerrillas representing the old, pre-War elites. Stalin sat that one out, abandoning the Greek people and their Communist champions in return for what he believed would be a free hand in Eastern Europe, but even there, on ground won by the might of the Red Army, the Western Allies, especially after the death of FDR, began badgering him with a lot of crap and nonsense about the "freedom of Poland" and other garbage they had absolutely no idea of the complexities of. As the Americans and British began cozying up to the defeated Nazis, many of whom had committed horrific atrocities in the U.S.S.R. and Eastern Europe, Stalin began to feel that he was again being surrounded by a capitalist-backed series of pro-Western, pro-business regimes run by the same pre-war elites which had easily flocked to Hitler's banner. This was followed by Stalin making sure that his grip on Eastern Europe was solidified, while the Western Allies, which had agreed to all of this at the Yalta Conference, began bitching, griping and threatening their former Soviet Ally notwithstanding Stalin's acquiescence his former Allies' intervention in the Greek Civil War.
So in a nutshell, while FDR and his VP Henry Wallace had believed in U.S.- Russian cooperation, under the Cold War policies of Truman and Acheson, these policies were overthrown and replaced by Cold War hostility and never-ending wars of aggression, basically a betrayal of our former Allies and an embrace of everything that we and they stood against, that continue to this very day despite the "collapse" of communism. Essentially this policy was a product of the so-called "military-industrial complex" referred to by Pres. Eisehhower in his farewell address. A good expository outline of the military-industrial complex can be found in "The Power Elite" by C. Wright Mills. There is no question in my mind that in its international relations, since the death of FDR and the electoral defeat of Henry Wallace in the 1948 Presidential election, it's been downhill all the way for the U.S.A.
