Acually, here in NYC you can find birch beer, but I haven't found phosphates, which I did run into in rural Pennsylvania, near the Delaware River about 30 years ago.
Birch beer is similar to root beer, but is a little stronger in taste and has a very slight taste of wintergreen.
The real local favorites here in the Big Apple are Doctor Brown's Celray Tonic, yep celery soda, and a very nice coffee soda, I think called Manhattan. Dr. Brown also makes cream soda. Is that a regional soda also? I know Boston is known for "Moxie" a brown soda which you have to be born in New England to enjoy.
What the heck, we were college students back then and not very worldly; we thought everybody had the same tastes as we did.