From an outsider, it really feels like there's no middle ground in American politics. You either commit yourself to the full slate of beliefs for one side, or you're the "enemy".
I hope that Americans on both side start to see that either they need to tone down the rhetoric, work together and reach across the aisle, or just take the tough step of a national divorce due to irreconcilable differences.
Part of that is to stop giving a voice to the insane rhetoric, and stop electing *waving vaguely*.
The truth is the US has been seen periods of extreme rhetoric and even political violence, including most obviously an actual civil war, and also key periods like the labor movement and civil rights movement. It will happen again even if things cool.
Political violence and assassinations are obviously terrible and should hopefully not happen as debate allows consensus or at least compromise to be reached, but the reality seems to be if you allow the people a stake in their government, passion and anger will be instilled in some subset of those people cause government policies have real world implications, and the end result is extreme acts, many of which are detestable like this one. I don't see a way forward other than to prosecute crimes and let the debate rage on.
The best we can hope for is that the convulsions will be short and sharp and no foreign power takes advantage of our convalescence. In 1945 the Germans learned a hard lesson about fascism, and learned it well; we can hope that Americans will learn something too, and at less cost.