Stephen Walt reminds us that a single policy can affect more than a single country:
[I]f a few other states were thinking a bit about acquiring nuclear weapons and took a look at Iran's experience, and then concluded that pursuing the bomb just wasn't worth all the aggravation, then Iran's experience might have broader positive effects. It teaches that if you try to get a bomb, you'll face censure, demands for inspections, lots of diplomatic hassle, and maybe even mildly inconvenient economic sanctions. … So while sanctions may have failed in dealing with a hard case like Iran, they may have helped reinforce global nonproliferation norms and thus persuaded a few other states not to start down that road themselves. And if that is indeed the case, then "Policy X" (in this case economic sanctions) may have a more positive "net effect" than a simple focus on Iran might suggest.