I've seen a handful in CA. Usually they're visible from a large distance, given the flashing lights and traffic backup. Sometimes they'll even have signs up a few blocks in advance warning about the upcoming stop.
I used to commute in a red sports car at midnight, and my direct path to the freeway and home was regularly blocked by a checkpoint. The officer started to instruct me on being checked, and I whined that I was tired, and he waved me by. Town was notorious for interfering with traffic with their checkpoints and speed enforcement. Sometimes checkpoints were disclosed on radio. Looking back it’s amazing they didn’t cite me for my confessed exhaustion. Also this was a long time ago so YMMV.
Varies from state to state - in some states they are illegal under state law or state constitutions, etc. Looks like they're illegal in MI.