the fact Christian nations fought two World Wars
That's a stretch.
According to wikipedia, the top ten belligerents were:-
By total deaths:
World War 1:
Russia - Christian (Orthodox)
Ottoman Empire - Muslim
Germany - Christian (Protestant/Catholic)
Persia - Muslim
Austria-Hungary - Christian (Catholic/Orthodox), Muslim
France - Christian (Catholic)
British Empire - Christian (Protestant/Catholic), numerous others
Italy - Christian (Catholic)
Serbia - Christian (Orthodox)
Romania - Christian (Orthodox)
World War 2:
Soviet Union - Atheist, Christian (Orthodox)
China - Confucianist, Buddhist
Germany - Christian (Protestant/Catholic)
Poland - Christian (Catholic)
Dutch East Indies* - Muslim, Hindu, Buddhist
Japan - Shinto, Buddhist
India - Hindu, Muslim, Sikh
Yugoslavia - Christian (Catholic/Orthodox), Muslim
French Indochina - Buddhist, Confucianist, Taoist
France - Christian (Catholic)
By military casualties (arguably a better measure of who "fought" the war):
World War 1:
Germany - Christian (Protestant/Catholic)
Russia - Christian (Orthodox)
France - Christian (Catholic)
Austria-Hungary - Christian (Catholic/Orthodox), Muslim
British Empire - Christian (Protestant/Catholic), numerous others
Italy - Christian (Catholic)
Ottoman Empire - Muslim
Serbia - Christian (Orthodox)
Romania - Christian (Orthodox)
USA - Christian (Protestant/Catholic)
World War 2:
Soviet Union - Atheist, Christian (Orthodox)
Germany - Christian (Protestant/Catholic)
China - Confucianist, Buddhist
Japan - Shinto, Buddhist
USA - Christian (Protestant/Catholic)
UK - Christian (Protestant/Catholic)
Italy - Christian (Catholic)
Yugoslavia - Christian (Catholic/Orthodox), Muslim
Romania - Christian (Orthodox)
Poland - Christian (Catholic)
Certainly Christian nations were
included, but it's not clear at all that they
dominated the ranks of the beligerent nations, much less that "Christian nations fought two World Wars". I think you could make a case that "Christian nations fought the First World War", if you look only at military casualties, and treat the Ottoman empire as a very minor player.
* The Dutch East Indies were led by a Christian (Protestant) colonial
power