There seems to be resistance to discussing this topic, from the left obviously, but also from the national media which is mostly made up of people on the left. In addition, the left has the extremely well-funded SPLC which routinely provides information and quotes to reporters about the threat of right-wing violence. But the right lacks a group dedicated to highlighting the threat of left-wing violence. The result is that you have a few articles about the growing trend of left-wing political violence, but nothing compared to the outpouring of newsprint we saw after the Tucson shooting (which it turned out had nothing to do with the political right).
The trend won’t go away simply because the media refuses to connect the dots. On the contrary, lack of attention guarantees this problem will continue to grow. We will eventually have a national discussion about this but, as in Germany, I suspect it won’t happen until something even more horrible than the Alexandria shooting takes place.