Future historians and archeologist will attribute fall of American empire to this or that disaster or war. In reality it is getting to the point that defending what we collectively have is less important than sticking it to the other side is what going to bring it down. Collectively, so far, right have done a lot more damage than left - just look at the office of POTUS for evidence.
Yeah, Trump has been pretty damaging. Honestly, doling out exact proportions of blame feels a bit like re-arranging the deck chairs on the Titanic at this point. Or trying to figure out whose responsibility it was to dodge that iceberg as icy waters begin seeping into the bridge.
The wacked right's electoral success has been greater in recent years, but the outsized corrosive effects on education and media by the psycho-left cannot be discounted either.