In the USA the law changes from state to state and enforcement from county to county. Many "Red" states have "Stand your ground laws" which apply even outside your home. "Castle" doctrine is your residence or recreational vehicle "home". In California, they have to come through the door (threshold). Some California DAs push to have the homeowner withdraw further inside before using violence.
However, if the homeowner has been a crime victim, or has been watching a steady stream of crime TV and have a gun, they are thinking about RIGHT NOW, not what the local District Attorney MIGHT think....add in some dementia or a cocktail...and it could be "deep sleep time" for an unexpected visitor.
After these recent unexpected visitor shootings and the mass Kingdom Hall shooting in Germany, I would hope most JWs would re-think door-to-door protocols. Folks an imaginary angel will not protect you.