The reality is that all of central Africa is becoming a Christian/Muslim battlefield. Sadly when the two cultures come in close physical proximity, there is no peace. Somehow the Africans will have to work out a consensus and modus vivendi. American mothers did not raise their sons to die in Africa.
I do understand the difference between bad things happening someplace and an American duty to intervene in that place. We do have a military duty to help get our own American citizens out, but once that's done, South Sudan is probably going to be on its own.
I hate to say it, but the Chinese are probably the best hope the Christian population of South Sudan has right now.
China wants oil, it needs stability in both Sudan and South Sudan to get the local oil, and for China's own reasons (i.e, the Uighurs), China is very concerned about radical Islam and would prefer to see their oil coming from people who have an economic interest in selling oil rather than seeing a tribal and religious war disrupt those oil supplies.
In other words, China does have a direct economic interest and may force a settlement.
But China is not known for respecting any sort of standard of human rights or constitutional government in imposing that settlement. Orderly government and economic progress, not freedom, is what motivates China.
Perhaps the best-case scenario under a forced Chinese settlement would be the Chinese installing some sort of business-oriented technocrat from the black Christian population of South Sudan and giving him the military muscle necessary to run an authoritarian government — and there are a lot worse possibilities for a Chinese-enforced settlement than that.
African wars are brutal beyond anything we’ve dealt with complete with child armies and forced cannibalism.