why is it believed much remains to be done before black a mericans enjoy full equality

在美国黑人获得完全平等之前，为什么大家还是认为有很多待做？
Because the U.S is still a white-dominated nation in every aspect ( politically, socially, economically....), as a minority, in order to change this situation, black Americans still have a long way to go.

because there are many discriminations against them