There are areas in the Western US where livestock is allowed to free range, and if you injure an animal or hit it with a car, you are responsible for restitution to the owner. These areas are marked with road signs btw and are usually on 2 lane roads. So yes, unless you fence your property in these areas they can roam your propertyHere in the USA, the owner of the animal is responsible for keeping it contained. Especially in rural or urban neighborhoods where other people are affected by their neighbors roaming animals. The owner can have their animals taken away and be fined. As they should be. I repeat, nobody has the right to let their animals roam onto someone else's property.