Years ago I chatted with a border guard from another country about their job (while they were not working). Not having a phone nowadays would be considered "strange" enough to flag you. If you're not a citizen of said country, it could even dramatically increase the odds of disallowing you entry. Often this would prevent you returning for a set number of years.

At the end of the day, it's always best to just not have anything "bad" on your devices. People have been caught up for all numbers of "innocent" reasons (pictures of their kids in the bathtub, ancient photos in their albums of themselves doing illegal things such as drugs or underage drinking, text messages or browser history disparaging politicians the border guard may support, porn in your history) that can give a border guard in a bad mood good reason to ruin your day.

I personally don't want my phone data hoovered in and analyzed or marked, even though I don't really have anything to hide. I don't care enough to do anything about it, but if I did I would probably have a second travel phone with a curated amount of data, apps, accounts, etc.

The last time I tried to do that on a trip to Germany, admittedly many years ago, I found I could not get phone service without a local address.

If you can, just avoid ever entering the US at all.

It has been standard practice for some time now in some European companies.