I think one of the primary reasons for the failure of both the U.N. and NATO opeations was the amount of effort the involved member nations put into peacekeeping operations. For the most part, the only nations that had the sufficient resources and experience within the continent was G.B., France, and Germany and neither of them wanted to be stuck with the job of picking up the Lincoln logs of some former socialist state* and expected the bigger buddies across the pond to intervene.

The same reason can be applied for Canada, but for the U.S., there was most underlying reasons. The first was that the Cold War was over and downsizing and redeployment of forces to tackle the growing threat of terrorism Middle East. The second was the military will of Bill Clinton. His first military event at the beginning of his presidency was the infamous "Black Hawk Down" event that had a lasting impression on him and his use of military force in situations that would require such. The third was, like everyone else, that no one wanted to be pulled into a growing mess that had no benefit whatsoever.

In the end, growing media attention, the increase in public awareness, and confirmed revelations of genocide including the humilating loss of the Dutch controlled U.N. Safe Haven resulted in the forced intervention from most of the major western powers that so desperately did not want to get involved.

Edit:* Referred to Yugoslavia as a former Soviet satellite state in which it wasn't. Thanks to u/BezStraha for the heads up.