In the same way that you can't necessarily trust the water quality of any given campground or RV park you stay at, you don't always know what kind of water pressure a place will have. It's just one of those variables you have to account for.

Unless you like the thought of waking up one day and stepping into water on the floor because of a burst pipe, you need to get an inline water pressure regulator like this one. It's made of brass and has a built-in gauge for checking the pressure coming out of the ground before it hits your camper. If you want to set it to a max PSI, you just turn the knob/screw on top until the gauge says what you want it to.

This isn't one of those, “Oh, that'd be nice to have” kind of things — treat it more like an essential piece of your kit, because it is.

There are like a hundred of these you can buy for $25–$30 that all look like exactly the same but with different branding, so I wouldn't stress too much over which one you choose. I'm only linking this one because I like the "Twinkle Star" company name ¯\_(ツ)_/¯