A post of mine from a few months ago (it was focused on refuting the idea that the CSA would join the Entente at an early stage, but I think her joining the Central Powers is at least as unlikely):
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Like others, I doubt very much that in a CSA-wins world, the next fifty-odd years would leave European politics completely unchanged so that the World War breaks out with the same belligerents at the same time, etc.
But let's assume that somehow it does. There is no reason to think the CSA would join the Entente. Like Yankees, Southrons would want to stay out of that bloody business overseas. The notion that gratitude to the British for helping them win their independence (if indeed Britain does so) is going to guide their foreign policy a half century later is unrealistic. Quite likely they will have had quite a few quarrels with the British--for example the UK may try to stop Confederate expansion into Latin America. FWIW, in OTL Southern opinion during 1914-15 in OTL was quite anti-British--as I wrote in soc.history.what-if some years ago: "There *was* considerable anger among Southerners over the blockade preventing cotton from reaching Germany. In 1915 it was thought that Southerners might join with German- and Irish-Americans in Congress to demand an arms embargo in retaliation for the British suppression of the cotton trade with Central Europe. John Sharp Williams, the pro-British Senator from Mississippi, spoke truthfully when he said that every politician in the South had to be anti-British. On June 28, 1915 the Georgia state legislature petitioned President Wilson to take every measure "diplomatic if possible, retaliatory if necessary" to open American trade in cotton with neutral European ports. However, the British defused this problem by a secret agreement for the British government to buy enough cotton to stabilize the price at ten cents a pound. See the discussion in Arthur S. Link, *Woodrow Wilson and the Progressive Era 1910-1917* (Harper Torchbooks edition 1963), pp. 170-2."
The CSA may eventually join the war against Germany but probably only at about the same time and for the same reason the USA did: the German resort to unlimited submarine warfare--including killing Confederate citizens on Confederate ships.