Guns, the amazing fact that bare nipples in a TV show can cause a national scandal while it's no big deal at all if a kids show like the Simpsons can contain absolutely ridiculous amounts of violence, gore and other highly problematic behavior, not just bending but outright stomping over rules being commonplace in virtually all major police (e.g. Law & Order, NCIS, Cold Case) and medical (e.g. Dr. House) shows and movies, "rolling coal" on bicyclists and road rage in general being a thing...
Torture being accepted so widely as well also ties in with what makes the US penal system so unique among Western ones - everyone else has switched their penal system to rehabilitation and prevention (i.e. try your best to make sure that felons don't commit more crimes in the future), whereas in the US you don't just have stuff like ridiculous prison times or being released with no assets, no help, no nothing after a lengthy prison stay, it's widely accepted to the point of being the butt of jokes that you get raped in prison ("don't drop a soap bar") or that you have to deal with massive overcrowding, roaches, mold in food... in any civilized society, the courts would intervene immediately for such reports, but in the US? Nothing has changed there in decades, partially of course because the US political system is dysfunctional, but IMHO more because people accept inhumane treatment of people who "have done something wrong, so deserve it".
And to add on the 9/11 thing: the US is already a deeply traumatized nation at its core. Stuff like MKULTRA, the Vietnam war or the 1st Iraq war never got addressed and dealt with as a country in a healthy way - and completely forget about the even older stuff like slavery or the discrimination of e.g. Japanese-Americans during WW2, there's more than enough politicians in power who do everything they can to repress even teaching about that! 9/11, Afghanistan and the 2nd Iraq War, the multitude of financial crises since then - that also didn't get dealt with.
How can anyone expect healthy attitudes from a society that never allowed itself to heal from its past?