Nope, even intrastate flights are subject exclusively to federal jurisdiction.

I've only recently turned 18, and have never had an issue being served alcohol previously, both when flying with parents and family or when flying alone - even on American carriers. Similarly, in lounges, I normally have some wine/beer/champagne. Also never had an issue there.

Even on a recent school trip, some friends and I had a few drinks with dinner (it was a TATL flight). No questions asked from CC.

When flying with parents, I think it's extremely unlikely that one would be denied the right to consume alcohol. When travelling by oneself, there's a higher chance of being denied, but I'd say it's still very small. Just as long as you dress relatively formally/ don't look really young.

I think the highlight of my son's trip on the testing flights for the A380 was asking for - and getting a can of Heineken at the age of 15 on Air France