I've been pondering this off and on. We visited some friends in the USA (midwest if it makes a difference) a while ago. They had just bought a puppy, which came with us on a short walk one day. Not knowing the area we walked down a dead end on their estate, and as we turned around to come back saw a wolf the biggest husky I've ever seen, sitting under a tree watching us, completely unfenced in. Friends' puppy was very reactive and aggressive to other dogs, so we got out of there asap without him spotting - and upsetting - the other dog. Apart from our blood pressure, all was fine, but it was the biggest rush of fear I've ever had.
We asked our friends about it and apparently where they live (stereotypical US affluent estate with big front lawns), invisible fences are really common. They pointed several out to us during the rest of our trip and were adamant that the fences work 100% of the time and they are a great idea. Having said that, they are not the best dog owners I've known (I mean this factually, rather than disparagingly - mixed messages, finding biting and aggression funny, only letting the puppy out to toilet on the lawn (sometimes) and not walking him - I ended up Googling a lot about the breed as I felt so sorry for him and he should have been getting 2x short walks a day at that age - hence us taking him for a walk), so I've wondered since if this is true.
I've never seen them in the UK (to my knowledge) and thought knowledgeable posters on here might know why - is it that gardens in the UK tend to be fenced in / smaller, or are invisible fences thought to be cruel (I've seen mixed responses to e.g. training collars, which I think operate similarly)? To be fair I've been in other places in the USA and also not been aware of them, but those places have either been much more rural, or very urban, not suburbia.
Many thanks to anyone who can shed some light.