We don't have a cat door. We had a large one many years ago but got rid of it when we found our teenage daughter was using it to sneak in after hours. Our one remaining cat stays pretty much indoors or on the upstairs balcony.

Haven't been bothered by the raccoons around, but several possums have tried to get in to sample our cats' dinners, like when we left the back door open while gardening.

My mother-in-law lives in SF, where houses adjoin each other without setbacks. A few years ago a mother raccoon managed to work her way between her house and the neighbor's and set up housekeeping a few inches from the head of M-I-L' s bed. Made quite a lot of racket during the night.   A number of things were tried without success, short of tearing out the wall. The thing that finally worked was getting a cheap transistor radio, setting it to a local hard rock station, and lowering it down from the roof into the nest area. By the time the battery had run down the raccoons had moved on, apparently for good.   Nonviolent and effective.