The problem is that the UN doesn't let anyone use actual military force against the bad guys (because the UN includes so many countries supporting the bad guys). All this leaves is the few countries powerful enough to not care what the UN thinks, which basically boils down to the US - and the US has been burned badly in the past due to internal imcompetence / strife of its own, and is currently limiting itself to military actions that promote the US agenda. The problem isn't so much the military (or even the government), but rather the left-leaning media that does everything it can to bad-mouth any military action of any sort, and forces so many layers of oversight that the military is hamstrung.
Btw, you should note the fact that it's Sudanese Christians who are primarily being killed off. Christians don't become terrorists when the going gets tough, and in point of fact, the majority of terrorists are middle class and educated and fairly well off, so I don't see how the whole underprivileged = terrorist argument works anyhow. If we help the Sudanese, it will be because it's the right thing to do, not because it in any way prevents terrorism.