To clarify, police officers are not civilians...they are constitutionally sworn to an oath similar to the military oath to uphold the US Constitution and State laws. By taking this oath, they are given certain authority that civilians do not have. They can effect arrests, use force to effect arrest, protect themselves or the public at risk by using force up to and including lethal force, and are able to detain and investigate suspected criminal behavior for reasonable suspicion (not to be confused with reasonable cause, which is the standard for arrest). Police are granted far broader powers than civilians. With that comes responsibility to use discretion when possible to diffuse situations rather than escalate them, If someone actively resists lawful efforts by an officer, that is when escalation of force comes in to play. Once a citizen escalates to a level of violence where they endanger the police or public with weapons, police are trained and authorized to use the level of force to overcome that. That may not sit well with people, it is, in fact, the law of the land. I doubt highly the British system would work in the US. There are far too many weapons available here versus other countries. Gun control is an entirely different discussion, but what we currently have to deal with is a glut of guns in the streets. Unarmed police would be ineffective against that scenario. Training and selection is the best answer to the current situation. Until we have RoboCops, mistakes will happen and emotions will cause bad decisions.
I would encourage anyone who can, to avail themselves of doing a citizen ride along with their local police department. It will give you an interesting perspective of what happens on a daily basis doing the job. I guarantee you will see things differently...