I am not sure who is in the presidential office has any real bearing on this since Reagan did when he released all the mentally ill on the streets en masse. Might as well blame George Bush Sr for the Mt Pinatubo volcano in the Philippines.
That said, Enron kind of hit this right. Gun access is part of the problem, though not all of it. And the same is true for mental health.
Since most people do not have their children killed in a school shooting, it's convenient and easy to for them to resist any risk of changes to their gun ownership rights while make-pretend believing that state of armament protects them from harm. (As with the TSA, it's always about the emotional illusion of control ... rather than statistical likelihoods that might suggest they are not Arnold Schwarzenegger in a Hollywood movie.)
So any flinch to make a change comes with all sorts of bellyaching about how change always carries a risk of things possibly failing. Which is true of any change. Even if there's a real potential of making some things better. So the excuse is that since change could have potentially negative effects, let's do nothing because nothing is better and we love the status quo -- even if someone else's kids keep getting killed. Which means more dead kids in the news every month. That is not a sane response.
On the other side we have mental health. Going back to Reagan, it is misunderstood and treated suspiciously at a policy level -- and is not seen as a broad social good for everyone in society. As such, any organized attempts to validate and treat are often perceived as socialist medical programs that bloat government when isolated, privatized measures should be preferred. Add disengaged parents and a lack of your typical social nets of neighbors who know each other, people who attend churches or other community groups together, etc., and we have unsupervised loners who are time bombs. Once again, this is not a sane response.
They are, btw.
I'm still with Enron in that it's both gun access and how we handle (or not) the mentally ill.