How Does Descartes Solve the problem of Cultural Relativism (or not)?

Many people in what we’ll call “liberal” culture in the United States believe that this country is fundamentally racist, since slavery was a central part of our society when our Constitution was written and was written into that document (through the 3/5ths compromise).  Other people in what we’ll call “conservative” culture in the United States believe that this country is fundamentally egalitarian, founded on the belief that “all men are created equal” and that all people can flourish here if they work hard (in other words, the US is a meritocracy).