If you're referring to ICE, that's gross hyperbole, and honestly a little insulting to people who live / have lived in regimes with an actual secret police.

The US is still a rights-based state, which means that when they arrest someone (legitimately or not), lawyers and human right advocates can eventually track them down.

When a secret police disappears someone, they actually disappear. Families can spend years wondering if their loved one is still alive, or was murdered by organized crime, or ran away, or was secretly taken by the state. The US these days is pretty bad, but it's nowhere near that bad.