The Biblical Basis for a Genocidal Civil War in America

You missed the word “yet”.

The thing to understand is America has vast marketplace of differing and merging theologies thanks to Separation of Church and State. The modern white right wing evangelicals are descendants of mostly poor, ill-educated people in the South and Midwest. Their churches were Baptist, Methodist, Presbyterian, Lutheran, Dutch Reformed, etc., most from off-shoots of the European reformed churches. 

Other denominations broke away from these main stream congregations with the Fundamentalist slant provided by a group of Presbyterian theologians at Princeton Theological Seminary in the late 19th century. These teachings became part of their theology. The Depression hit everyone in these regions (that had always been poor) bad, but in particular it devastated the working class evangelicals. 

Another group of 19th Protestants, descended from the Midwestern Millerites, focused on End Times using the writings from the Bible with commentary and compared them to current events in order to predict when the end will happen. The Scofield Study Bible was the most popular one. The Ryrie Bible is a popular today.

Most of the mainstream churches rejected much of these new concepts, but many within MS churches accepted it and broke away to form new, more fundamentalist congregations. The End Time people used to be a small minority, often located in Holy Ghost churches, but recently many of these disparate churches experienced a mutual cultural drift thanks to tent revivals, radio, then TV where fundamentalist theology and End Times or Premillennialism and Amillennialism eschatology commingled. Millennialism was not a thing in the Southern Baptist Church until recently. Nor is the neo-Calvinism some now preach.

Then in the late 70s, Falwell formed a political wing called the Moral Majority, followed by James Dobson’s Focus on the Family, and the Christian Right. They began the politicization of these churches.

Today there are a lot of megachurches were these concepts fly high in a non-denominational setting. That is, the pastors are not associated with any church conference and they can pick and choose what the preach. (Not all megachurches are political.) 

This is the messy behemoth that forms the religious core of Trumpism. 

This is an ad hoc outline. To find out more, read up on The Great Awakening, the Burnt Over District (Mormonism sprang from that) and the Third and Fouth  Awakenings. Most of modern American-style, fundamentalist/End Times Christianity form from this events.