In the grand scheme of things, 100,000 deaths is a non-event for a government representing over 300,000,000 constituents. Almost 6 times that many people die from both cancer and heart disease each year. Where it becomes a problem for governments is when there's bad PR. They focus their attention on terrorism because it commands the national attention, not because it's a significant threat. While the abuse of opioids is no doubt a problem, it's getting government attention now because of media scrutiny, not because it absolutely needs to be solved by government.
Humans are terrible at estimating risk. We seem to do it by attributing it to the ease which we can recall an incidence of something similar happening. This may have worked well when we were part of small tribes, but it's terribly adapted to a world where every unusual, capricious event is is broadcast nationally and the mundane, common dangers receive very little media attention.
You can see this with the current debate over guns. Now I favor the liberal position of drastically increasing gun control, but only around 11,000 people are murdered with guns each year and another 22,000 or so kill themselves. That's around a 1/30,000 chance of being the victim of gun violence. Those deaths may be largely unnecessary, but we should still have the perspective to realize that they're not a significant threat to our health.