About 6 Months before the genocide began, US forces in Somalia suffered 20 killed and 70 wounded in the Battle of Mogadishu. These were the most significant operational casualties the US had suffered in some time, post Vietnam there had been only a handful of comparable events, the invasion of Grenada, the 1983 Beirut Bombings, etc. Congressional Republicans capitalized on the Battle of Mogadishu, it was a huge headache for the Clinton administration, not least because George H.W. Bush had actually initiated the US intervention in Somalia, (people often seem to forget H.W. Bush was a strong supporter of the UN). Public opinion turned sharply against humanitarian interventions in Africa, Clinton immediately ordered combat operations to cease and a timeline established for withdrawal of all US forces.

So Clinton and his foreign policy team wanted little to do with Rwanda or any other intervention in African civil wars. This top-level political calculus was compounded by a lack of institutional knowledge about Rwanda and the ongoing civil war in both the U.S. State department and the Pentagon. A problem further compounded by bureaucratic bottlenecks which prevented the small number of personnel familiar with Rwanda from being heard or reaching top-level decision makers.

The US Ambassador to Rwanda, Rawson, who normally would be a key figure in shaping the US response and engaging the wider processes of the State department, seems to have been astoundingly naive and failed to sound the alarm on genocide or realized what was happening, and then was evacuated from the country with his staff early on in the genocide. Congressional figures, such as Bob Dole, who were vocal about intervention in Yugoslavia, never took an interest in Rwanda. There were also other humanitarian disasters, in Bosnia, Haiti, and elsewhere that were happening at the same time and for a variety of reasons received the bulk of US attention.

This failure was not limited to the US, The UN peacekeeping force in the country, roughly 2,500 was underfunded, under-equipped and was left without orders by the UN at crucial points. Kofi Annan, who headed the UN peacekeeping office at the time forbid the UN forces from raiding interahamwe (Hutu militia) arms caches in the period before the genocide, and generally constrained efforts by the UN commander on the ground to do just about anything.

It is also worth remembering that the situation on the ground in Rwanda was fluid. There was a ceasefire in the ongoing civil war when the genocide began, but the rebel RPF controlled a swathe of territory in the North of Rwanda. When the genocide began, the RPF dropped the ceasefire and began to advance, ending the killing of Tutsis in areas they gained control of. But a second wave of killing, a counter-genocide occurred in the areas the RPF took control of. The extent to which genocidaires or merely innocent people were killed in the counter-genocide, and the extent to which the RPF conducted, enabled, or turned a blind eye to the counter-genocide is heavily contested. US policymakers really seemed to struggle at the time to understand the dual nature of the conflict, as a renewed civil war and ongoing genocide. But some seem to have genuinely believed these were combat deaths in a civil war, and had no desire to repeat Somalia. US ambivalence was also enabled by history, there had been previous smaller scale pogroms in Rwanda, a wave of killing in the 70's, and a killing of several thousand in the early 90's. The initial reports of thousands dead were easy for some policymakers to dismiss as just another outbreak of internecine violence.

Also unlike Yugoslavia, NATO was not united on Rwanda. France had strong ties with Rwanda, Mitterrand considered it part of 'La Francafrique' and had close personal ties with President Habyarimana, to the extent that their sons were friends and partied together in Paris. The genocide began after Habyarimana was killed when his jet was shot down. But it was his spouse, Agathe, and the circle of people around her (the Akazu), who are believed to have largely planned and orchestrated the genocide. France not only largely ignored the reports of killing, but launched a controversial intervention of their own (well, 2500 French and 32 Senegalese), 'Operation Turqoise" during the period the genocide was ongoing. These forces established a "safe zone" in the west of Rwanda, but the safety in this case was largely against advancing RPF forces, not against the genocidal militias. The role of French forces in the genocide is highly contested, there aren't major accusation that the French forces personally killed Tutsis. Rather the French are accused of slowing and halting the RPF advance while doing little to stop ongoing killings of Tutsis in the safe zone they established, and allowing the genocidaires to escape to the DRC. The US had followed France's lead to a certain extent on Rwanda, they had only supported the UN peacekeeping mission after French assurances it wouldn't go sour. The remote possibility of a US intervention was made more remote by the fact that it would have been an intervention at odds to the French one, or hamstrung by a NATO ally trying to allow the previous regime to retain power or a seat at the table.

Another facet is that there was very little in the way of video footage coming out of Rwanda, there were NGO reports but most journalists had fled the country or were locked-down in Kigali. One of the brutal ironies is that after the genocide ended and the RPF consolidated control over the country, there was extensive TV journalism of the refugee camps in the DRC, which galvanized public opinion in America and elsewhere and provided enough public pressure that the US government airlifted massive aid to the refugee camps. Among these Rwandan refugees were the genocidal militias which had escaped Rwanda, and many of these camps were effectively controlled by Hutu militias until the first Congo War. One can see in this how the rise of the Camera phone might shape more recent foreign policy, and how video footage can make something 'real' to the public. But at the time it limited public outcry, and groups such as MSF and Human Rights Watch who were apprised of events on the ground lacked grassroots networks to stoke public calls for intervention. Whereas nowadays a single phone video of an atrocity might go viral, the information ecosystem of 1994 was very different.

The final major contour here is that the environment and norms for foreign interventions were very different in the early 1990's. The US war on terror and the AUMF which has underwritten it have transformed the exercise of US military power abroad. Recall that the Yugoslavian bombing campaigns were highly controversial because one was done without UN security council authorization under the aegis of NATO. There were several high-profile US tomahawk missile strikes during the 90s. But nothing like the US small force interventions, regular drone strikes, and foreign operations that the 'war on terror' normalized. The US public was similarly considered highly-sensitive to foreign interventions, and Clinton didn't want to tank his party in the midterms or endanger a second term, he had a long list of other domestic and international problems competing for attention and resources

Congress, the presidency, the state department, the ambassador on the ground, the military, US allies such as France, the UN peacekeeping office, the voting public, and the media all dropped the ball in various ways; and ignored or downplayed the genocide while it was ongoing for a variety of reasons. The single largest factor to my mind, is that after the battle of Mogadishu, American voters signaled that they didn't view African wars as worth American lives, and politicians and policymakers took that message to heart; and America is a democracy, for better and for worse.

I would also worth considering the nature of the killing, by mobs armed with machetes and militias, also acted against US intervention. The US peacekeeping doctrine which was developed post-Mogadishu was exceedingly risk-averse. The NATO interventions in Yugoslavia overwhelmingly consisted of airstrikes, with peacekeeping forces on the ground only after the bombing campaign has forced the opposing side to the negotiating table. Air-striking mobs of civilians armed with machetes presents a different scenario, and one should consider how effective a US response without "boots on the ground" would have been.

Samantha Power's article "Bystanders to Genocide" is an excellent primer on American decision-making concerning the Rwandan Genocide.

Powers also wrote a fairly accessible book "A Problem from Hell: America and the age of Genocide" about the US response to genocides throughout the 20th century.

/u/caic has previously written on the UN failure to do anything about the genocide in Rwanda

/u/gwenavere and others speak to the matter of French Complicity in the Rwandan Genocide

Some additional history of Rwanda and Hutu-Tutsi dynamics This provides some context but there are also some curious omissions and dubious history, so take it with a grain of salt