The correct answer is - The United States failed to intervene in Rwanda when Tutsi people were killed.
The official apology of president Bill Clinton in Rwanda was because the United States were indecisive about what kind of measures should they take or are they even supposed to take any measures, which lead to enough space and time for the genocide in Rwanda towards the Tutsi people to take place, so at that point of time any intervention was already too late since the damage was done.