The US is quite violent by developed world standards, and it borders Latin America, which is insanely violent even by poor world standards.
IIRC, of the 50 most violent cities in the world, 17 are in Mexico.
This means that a lot more people who have seen grisly things (beheadings by cartels etc.) are present in the US, and this raises the awareness about what could also happen in the absence of a police force.
Not really, but there's a long history of media that puts police on a pedestal in a fight against darkness.
The more cynical would call it propaganda, but I think there's more to it than that: it dates back to old westerns and draws from a rich history of hero literature. The police became a subject of that pre-existing tradition.
IIRC, of the 50 most violent cities in the world, 17 are in Mexico.
This means that a lot more people who have seen grisly things (beheadings by cartels etc.) are present in the US, and this raises the awareness about what could also happen in the absence of a police force.