As of yesterday the US has 1,121,097 deaths total and a death rate of 3,349 per million population. South Africa has 102,568 deaths total and 1,688 deaths per million.
Once again, you cannot ignore the transmission rate, which you have chosen to do entirely. Their transmission rate is 1/6th that of the US.
US - 307,901 cases per 1 million
South Africa - 66,661 cases per million
So of course their death rate per million will be lower. They have fewer cases.