tldr: there is the electoral system.
governments change because of who leads/ represents the people in their governments.
in the US, “the people” have little to no understanding of their government(there have been studies about this for the last 60 years), and because conservatives campaign on emotional bigotry, which is immediately hard-hitting and compelling versus waiting 2 years to receive a tax decrease(which works, but takes 2 years), undereducated and unsupported American citizens have been put into increasingly untenable situations where they are struggling to survive while working themselves to the bone and receiving lower compensation, and if an emergency arises, they are denied basic services.
when you have no other options to support yourself, murder becomes an option, since nothing else has worked and they are provided with no other options they are comfortable with.
there are some civil services, and the government can always change, regardless of what popular opinion fashions, but right now in the US you have a couple hundred million people desperate to survive in a country that provided survival wages, and now that they have reelected Trump and he’s already before even taking the White House began turning against unions and civil rights, those wages will probably lower again, living cost increasing and civil benefits decreasing.
out of 200 million desperate people, some of them are willing to take the most drastic measure because maybe it’ll make a difference, who knows.
i mean, lots of people know, but most Americans have been clinging to the edge of a cliff by their fingertips for years or decades, so they don’t have the perspective that others may.
shhhh. it just works.