Not quite true. There are 24 states that currently have "stop and identify" laws where, if a police officer has suspicion that a person has committed or is about to commit a crime the police officer may request identification. Failure to produce identification could result in an arrest.
This is also know as a "Terry Stop", named after a court proceeding Terry v. Ohio. During a Terry Stop, a police officer may also conduct a search for weapons.
In case you are wondering, Florida is one of the 24 states that has a Terry Stop law. California does not.
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Armand
It's the crime that is grounds for arrest and for the ID check. Not carrying ID is still not a crime nor grounds for arrest. In all 50 states.