There have from time to time been posts about natural boundary protection, the most recent one I remember being using wild roses.  I also have a barberry hedge, but it has too many gaps to be an effective barrier all the way along the road side.

The following example is from India, where a huge hedge for custom purposes was built.  Of course the plants might not be suitable where we are, but I offer it as a chance to think about natural barriers, especially if there can be some fruit obtained from them so serving both as defense and as a production addition to the larder.

The natural living barrier was described as "utterly impassable to man or beast", and snaked across India from the Indus River to the Mahanadi.

https://www.bbc.com/future/article/20210824-how-the-worlds-longest-shrubbery-vanished-without-trace - https://www.bbc.com/future/article/20210824-how-the-worlds-longest-shrubbery-vanished-without-trace