Cats and humans look at possessions differently. Cats don't recognize property lines and think any open area is theirs to roam. They don't understand why that flowerbed should be yours and yours alone. And if the hood of a car is unoccupied and the cat's looking for an up-high place to survey the world or grab a quick nap, well why not use it.
But unfortunately for cats, it's humans who make the rules in this world. And if we live with cats who go out, it's up to us to make sure they obey those rules. Our cats need to be good neighbors, not just out of courtesy to the humans who live near them but for their own safety.
I like to use electronic deterrents that startle but don't harm the cats. I find them more efficient. But there are also scents that repel cats. For instance, most cats hate the smell of lavender and anything citrus. And planting borders of coleus canina around your flowerbeds will keep most cats away.
If a neighbor complains about your cats encroaching on his private property, you should be the one to do all the work. Buy an electronic deterrent, set it up and monitor it to be sure it's working. Or scatter lemon rinds around every few days. Or buy and plant the coleus canina. That's the neighborly thing to do, and it's the best way to keep an angry neighbor from hating you and your cats.
My neighbor doesn't hate my cats, but he doesn't like them either. That's because Hadon, his pit bull, is afraid of my cat, Sizzle!