The United States already does this for some of those entering the U.S., including the electronic devices of United States citizens:

CAIRO—Egyptian authorities are combining cyberattacks with random searches of phones and laptops on the street, as part of a campaign to thwart online dissent fueling rare protests against President Abdel Fattah Al Sisi.

Source: Egypt Curbs Online Dissent With Street Searches: ‘He Asked to See My Phone’ – WSJ

I automatically delete Twitter tweets more than 30 days old. After Facebook’s privacy violations became apparent to all back in early 2018, I deleted about 9 years worth of Facebook posts. I then cut back on my use of Facebook, rarely posting anything to share with friends. Last week, I began curtailing my use of Twitter (which is mostly a wasteland of the perpetually outraged).

Government policies and actions are stifling online speech.

We do not remember what we may have said in the past, how interpretation of what was said 10 years ago might be different in the present (for example, the hand “Ok” symbol used forever to denote “Okay” has been redefined in 2019 as a hate symbol), and more. Leaving content online is an invitation to future trouble.

Besides, the half life of a Twitter tweet is about 15 minutes – meaning half of its views will occur within about 30 minutes. In a day or two, it will have disappeared from view. Similarly, a FB post half life is probably a day or two at best. Old content serves little purpose – it vanishes from view except for someone wanting to dig up dirt.

But even without posts on our accounts, are friends and follower lists may get us in trouble. I have two photography friends who are citizens of Iran – does that make me a suspect? Undoubtedly.