To ask where someone is from, or to express where you are from, are the following questions phrased correctly and in a common, normal way?
Je viens des Etats-Unis. Je viens (suis?) de NY. (I am from NY.)
D'où venez-vous ?
Je viens des États-Unis/de New-York is possibly ambiguous. It might just mean you are travelling from the US/from NY. Je suis de New-York is okay and means you are from New-York city.
I would suggest:
— Je suis américain, j'habite New-York.
Spoken (vous): Et vous, vous êtes d'où ?
Spoken (tu): Et toi, tu es (t'es) d'où ?
Formal: Et vous, d'où êtes vous (originaire) ?