Grisly or polar bear are clearly the most dangerous animals in North America combine that with how hard they can be to stop. When they are serious about doing you harm you have a problem
A family dog chasing you because of territorial behavior or just because you are moving is not in the category of a black bear . On the other hand a large feral dog that with a pack of 5-6 dogs can down cattle is a whole different level and can be just as dangerous as most black bears. this type of dog is faster, more agile than a bear and lacks the fear/respect of humans most wild animals have .