The Color of Compromise by Jemar Tisby. It's a brief, readable, sweeping history of the role of the American church in the development of racially oppressive systems, stretching from colonization through to the present day. It's a humble but prophetic word, clearly written out of love for the church and a desire to see true repentence, reconciliation, and restoration. This is a must read for all American Christians, especially those who, like me, come from Evangelical or conservative faith traditions that have historical been uniquely complicit in the culture's racist systems. Again, the goal and result of this book is not shame and guilt but empathy and humility.
I recommend "The Color of Compromise" by Jemar Tisby, as well as the podcast team he's part of, "Pass the Mic", if you really want to dig into the topic. It has a lot to do with the history and continued racism within the church, but there's a lot to that. Some of it's just the unwillingness of the white evangelical church to confront their past and seek true reconciliation.