For instance, if you walk down University Avenue in Berkeley you'll see all sorts of people engaged in various levels of borderline-illegal dickishness -- blocking the sidewalk, harassing passersby for money, standing on a street corner with a ghetto blaster on full blast, whatever. Police officers go past in their cars but don't stop unless something serious is happening. If they were patrolling up and down on foot then they'd have the ability to slow down and talk to the troublemakers and hopefully move 'em along.
I live in Houston, and most of my interactions with Houston police have been negative. The one time I encountered a cop on foot, I was walking on a concrete wall about 3ft high in the early evening in an almost empty park with a friend, and he ordered me off of it. Another time, I was with a girlfriend who reported a hit and run, who even memorized the license plate and had visible damage on her rear bumper. The policeman insisted on getting a description of the car, despite my protests that my girlfriend doesn't differentiate that information. Nothing was done. I also remember another occasion where, despite my neutral, polite, and factual answers, the policeman kept escalating his hostility.
How well cops treat males in the US has mostly to do with their evaluation of your social class in the first second.
http://www.nationmaster.com/graph/cri_pol_percap-crime-polic...
At 2.84 per thousand that's a bit more than the UK (2.04) but less than Germany, Italy, Portugal, Latvia and other countries.