Summary: The best critique of Christian Nationalism I have read, because Miller so clearly understands the reasons that Christian Nationalism can be attractive and reasonable.
There have been various books about Christian Nationalism; initially, they were all condemning, and more recently, a few made positive cases for Christian Nationalism. The Religion of American Greatness is a conservative (theologically and politically) case against Christian Nationalism, one that does mention but does not focus on Trump. And one that is generous in its assumptions about why some find the movement toward Christian Nationalism appealing.
His fifth chapter, Nationalism, Cultural Pluralism and Identity Politics, is a good example of where I agree broadly with the conclusions and disagree with how he got there. As a broad stroke, he points out the weaknesses of the Nationalist orientation and the methodology of using the state to maintain a particular cultural orientation over time. To illustrate this, he commends freedom of speech and the rule of law, which must be done for all to have a sense of fairness and equity. He uses the “Drag Queen Story Hour” complaint as an illustration and, I think, rightly critiques how it is used to stir up a culture war agenda. This brings him to consider whether Christian Nationalism is a type of identity politics. I understand this point, and I do not entirely disagree with it, but I think he misses the reasons that we need to repair past harm and how minority identity sociologically works. (Although he does have a stronger call for repair of past harm later in the book.) I believe that Christian Nationalists are acting as an identity group, but what needs to be teased out more is whether that identity group has justification in their complaint. (But that is more about sociology than political science.) Regardless of the accuracy of the complaints, his ability to take those complaints seriously is the book’s strength.