I've used my NEXUS card with mixed success. In Massachusetts, the ABCC list of IDs that licensees can use as "a defense to a charge of service, delivery, or possession of alcoholic beverages by a person under twenty-one years of age" only includes the following:
1. A Massachusetts Driver’s License;
2. A Massachusetts Liquor Identification Card;
3. A Massachusetts Identification Card;
4. A Passport Issued by the United States or a government that is officially recognized by the
United States;
5. A Passport Card for a Passport issued by the United States; and
6. A Military Identification Card.
(Don't ask what the difference is between a Mass Liquor ID and a Mass ID. I have no idea.
EDIT: I looked it up. Liquor ID doesn't require proof of residence but is only for 21+, Mass ID requires proof of residence and can be issued at 14.)
At least one venue rejected my NEXUS card as being not on the list, so I gave them my MA license since I didn't have a passport card at the time (though I do now).
That said, I'm very difficult to mistake for an under 21 person at this point and licensees aren't required to limit themselves to that list; they just have less legal protection if they don't and turn out to be in error.