It has been reported a great number of cases concerning racial inequality,such as in America a white policeman killing a black man screaming I can’t breathe by pressing his neck with knees,Asians being attacked frequently and so on.

1. 该句的主要错误，在于只有形式主语，没有真正主语。

2.  I can’t breathe，这是screaming 的直接引语，不能与叙述的文字一样呈现。应加引号 “I can’t breathe”。

改为：

It has been reported that there are a great number of cases concerning racial inequality, such as in America a white policeman killing a black man screaming "I can’t breathe"  by pressing his neck with knees, Asians being attacked frequently and so on.