I’m Mexican but I work in the US. I’ve been coming to the US since I was a few months old since I lived closer to the border. I’ve never been asked for my cellphone or anything personal. They usually asked for the reason to come into the country, evidence of said reason and (before my work visa) my ticket to get out of the country

That said, since a few years ago you have to tell them your social media handles when renewing your visa, and it has a disclaimer that omission can be grounds for denying the visa