I have a love-hate relationship with the notion of 'Christendom'. Its legacy is so mixed and so ambiguous. However, at its heart lies a fundamentally dangerous construal of the relationship between church and state.
Here is Meic Pearse commenting on the Thirty Years' War (1618-1648) in which Protestants and Catholic tensions in Europe burst out into terrible acts of violence.
"That such incidents have any place at all in a history of the Christian church is a condemnation, not merely of the participants, but of the entire phenomenon of a politicized Christendom whereby churches have, and claim, a legal monopoly on entire populations. The Thirty Years' War (like the Crusades or the Inquisition) is not an accidental product of this idea, nor an aberration, but its inevitable consequence." (The Age of Reason, p. 160)
Sadly I fear that he is correct. The same message comes out time and again in the history of Christendom in its diverse Orthodox, Catholic and Protestant manifestations. I hope that Africa does not repeat our mistakes here.
When it comes to church and state I find myself very sympathetic towards the Anabaptists and the later non-conformists. Free church, free state.