For the US, there are unfortunate precedents, Lebanon in the early eighties, Somalia a decade later.
Both were rushed and ill-defined operations, as these things usually are.
After the gory detail of Somalia on TV
screens, no way any US president, of whatever political colour, would rush to put troops into Rwanda six months after the 'Blackhawk Down' debacle.
With Sudan, the additional factor of it being a former Bin Laden stamping ground, so he'll still have assets there, which you don't want if you are meant to be providing aid, as well as that unfortunate episode of the Tomahawk missiles hitting what was said to be a chemical weapons facility, but most people now think really was a benign drug facility, as claimed at the time.
Foreign troops, especially US ones, won't be a welcome sight for many Sudanese.
All that is needed is short term protection for aid efforts and possibly safe zones, though the EU Rapid Reaction Force is sort of a reality, it is at present only really geared up to operate within the European continent, that will change in time, and Sudan is within the deployment capabilities now, as we are not talking about a major all arms formation.
Of course, that's if the Sudan government allows it, if they don't then try getting the UN to clear toppling them, which would need some US support, won't happen as the organization of African Unity would veto it.
So maybe the use of severe sanctions, or the threat of them, to force them to allow UN aid and protection in.
Again, guess who'd likely vote 'no' on this?
This means that the rather lazy retort of 'why don't the EU do this one' does
not really mean anything, as the political and diplomatic limitations I've described above apply as much to the US as to the EU.
Most UN operations are done with consent, grudging or not, with the local government of that area, they are the ones that do the real peacekeeping, sometimes like in Cyprus for decades, largely successfully.
They don't make the headlines.
Taking this a stage further, to maybe operate without local government consent, to make in the minds of many 'relevant', would need a big change of attitudes by a lot of people, in the EU, US and outside these sphere's of influence.