As others have mentioned, most Americans think slavery is terrible. If you were to suggest to a typical American that we repeal the 13th Amendment and allow people to own other people as chattel, the most likely reaction would be some kind of stunned disbelief. Most people would probably assume that you were making some sort of joke (and one in poor taste, at that).
However, to understand American race relations you need to recognize that they have little to do with slavery per se and everything to do with the decades of institutionalized discrimination that followed the end of the American Civil War. Throughout the American south African Americans were denied access to jobs and education. Their political rights were suppressed; often they were denied the right to vote. Lynching and other forms of mob justice were common. All of this was not just permitted but mandated in a body of law collectively known as "Jim Crow laws". Even outside the south discrimination, though not mandated like in Jim Crow, was still permitted and widely practiced.
This situation persisted officially until the laws began to change as a result of the civil rights movement in the 1960s. Even after the passage of civil rights legislation, treating African Americans as second-class citizens had become ingrained in many white Americans and has been slow to change. Moreover, decades of discrimination left a mark on black communities that persists to this day, leaving many African Americans understandably aggrieved at their situation and in some cases demanding restitution. Equally understandably, these demands and accusations have in some cases provoked backlash from white Americans who feel they are being held responsible for injustices committed in some cases before they were born.
In light of all this, the subject of slavery doesn't really feature centrally in American race relations today. It comes up occasionally, but there are a lot of injustices that are both more recent and more directly responsible for the hardships that black people face in the 21st century United States. These, along with contemporary issues like unequal treatment under the law, are the things that inform race relations today.
Finally, you asked about the teaching of historical slavery, and, well, it's complicated. The institution of slavery is a national embarrassment, particularly its connection with the founding of the United States. Many of the founders, including Thomas Jefferson, author of the Declaration of Independence, and George Washington, Revolutionary War general and first President of the United States, were slave owners. As a result, there is a tendency to whitewash the role of slavery in the early history of our country. Often it gets only a brief mention and is treated like a footnote. In some cases slavery has been expunged from history curricula altogether, as in the famous Texas textbook controversy; however, revisionism that sweeping is usually treated as a scandal when it occurs. I would say that in most places the trend is toward a more open recognition of slavery's role in American history, albeit with occasional backsliding.