In Germany, police is generally perceived as trustworthy, your "friend and helper" as the slogan goes.
I was surprised by the antagonism and belligerence in the US.
A few observations:
* guns certainly play a big role, and the risk of escalation.
* I wonder whether silly laws also play a role. For example: a 20 year old drinking alcohol, having a cold beer while watching a sunset on the beach, prostitution are all illegal if I'm not mistaken (or smoking a joint, depending on the state). So, in the US, the police might often be the killjoy. In Germany, those things are either officially legal, or in a gray area that the police ignores. So when the police comes on the scene, it's generally an actual crime or problem, and everyone is eager to help and cooperate and fix whatever real problem there is. In short, police have a relatively positive image.
* My experience with the police in the US was much worse when I was on a bike than when I was in a nice BMW. The issues of power differential, authority, lawyers, confrontation seem to loom much larger in the US than I've perceived them in Germany.
* With all these factors, employment with the police might seem a less attractive choice of work in the US than in northern Europe, so people with few other choices (or a penchant for exercising authority) might end up there more frequently than in other countries. This, in turn, could result in a downward cycle and a "besieged" mentality.
At any rate, I'd much rather interact with police in Europe or Asia than the US.