There are varying attitudes (in the US) with regards to the management of dogs. In my local area there is no lease law and as such it's not unusual to see bands of dogs roaming the town doing whatever it is that they do. Some people in my local area think it's quaint and "natural." I find it a problem for motorists, joggers, children and the dog. These dogs have threatened people in the past - but there has been no change in the law. The same also holds true for cats who wander and cause high % of damage to local fauna like birds, small reptiles, mammals etc.

It is not unusual to see any of these dogs run after a cyclist because anything which crosses their territorial path is considered an intruder by the animal. Until there is some common sense (and penalties) regarding the care of dogs outside we will have issues like this in the US.