"Why can't Americans implement a similar system to dissuade bears, cougars and coyotes from attacking humans in running trails?"
Coyote attacks? Against adults? Maybe if you have a small to medium dog with you.
You're chances of seeing a mountain lion, much less getting attacked by one is far less than getting attacked by a dog. Depending on where live, you might see coyotes. You have far more to worry about with dogs.
I had to fend off a dog 4 times in my 10+ year running career. I saw countless coyotes and never once feared them.
Rattlesnakes were my biggest concern.
Now if I lived where I do now when I was a twice a day runner, I would have been a little weary of mountain lions on morning runs. Two have been found dead hit my cars less than 2 miles from my home in the 14 years I've lived here (suburban area on the edge of San Diego - where there is a canyon route out to the mountains).
I've known runners who came across black bears. They seem more afraid of you, but I certainly would not want to run across one myself. Even hiking.