The role they exist to perform is maintaining the American empire and hegemony, and they've done a pretty good job of that up until ~this year.
'Keeping Americans safe' is not on their agenda. If it were, they wouldn't be sticking America's hand into Middle Eastern quagmires, like the one that radicalized OBL and provided a training ground for his friends and allies. If it were, they wouldn't be working half as hard in demonstrating to hundreds of millions of people that yes, America does, in fact, mean them harm, and is happy to inflict that harm on them.
'Keeping Americans safe' is not on their agenda. If it were, they wouldn't be sticking America's hand into Middle Eastern quagmires, like the one that radicalized OBL and provided a training ground for his friends and allies. If it were, they wouldn't be working half as hard in demonstrating to hundreds of millions of people that yes, America does, in fact, mean them harm, and is happy to inflict that harm on them.