I'm not going to try to characterize where these terrorists come from, by ideology -- they're dangerous, perhaps mentally ill men, very likely white, who for some god-forsaken reason have access to weapons soldiers carry into war zones. Republicans are morally responsible for them, for their refusal to pass sensible gun regulations, and those who vote against those regulations all have serious blood on their hands and their souls. (I wish I believed in souls, it would be useful here, but I don't.)
I'm not convinced the easy access to guns in America -- serious guns -- and the kind of trend above, and the Republican's push into fascism in the face of their terror of losing power due to demographic trends -- isn't going to lead to a dissolution (viz. crackup) of the U.S. in a few decades time, maybe even sooner. Add climate change and income inequality and (despite Biden) the lack of an adequate social net and affordable and universal healthcare system, and I'll even throw in the potential failures of the Ogallala and California Valley Aquifers and snowpack failures and early melt leading to water shortages in the Colorado River and Pacific Northwest...well, the world usually finds a way to squeak by. But not always, not without some significant and lurching change.