Evangelical Protestantism in Great Britain is very multiethnic, with a particularly high number of people from African or Afro-Caribbean backgrounds. Gregory Campbell has thrown into sharp relief the fact that the DUP and its electorate are wildly untypical, not only of British identity in general, but also of British Evangelical Protestantism.
Their only real connection or resemblance is to a declining section of that tendency in the white American South, of largely Scots-Irish descent. But even the most Anglo-Saxon of British Evangelicals are rightly proud of their tradition's role in the struggle against the slave trade. That could not be further removed from people who fundamentally still identified with the Confederacy. Fewer and fewer impeccably Scots-Irish Evangelicals in Dixie are like that, either.
Hey, ho. Irish Unionists have only ever, ever, ever been of any interest at Westminster when English Tories have needed the numbers to see off someone else for control of England. The present parliamentary arithmetic presents no such need. Instead, keeping control of England has necessitated, quite incidentally, a border down the Irish Sea. So the next time that the numbers needed to be made up, then they would have to find someone else. There will be no more Irish Unionists.