Did you EVER say "I'm a police officer/LEO/FBI/BATF/CIA"? If not...the act of flashing your valid driver's license is NOT "impersonating anything"...if the drunk/dumb kid INFERRED that you were, it is HIS problem...not yours or the States.
I advise you to get a SHARK lawyer...if his parents or the kid are behind this, then they have to admit UNDER OATH that their delightful cherub was ILLEGALLY behind the wheel of an auto...so he hangs for it! That should take the starch outta them...