"I'm from Japan."
出身（しゅっしん）is often translated as birthplace, but is actually considered the place you 'hail from'. Someone can have been raised in a certain locale and still lack that locations citizenship. 国籍 is one's nationality, ergo their citizenship.
If you're a military brat, しゅっしん would mean the location that you feel most attached to and spent the greatest amount of time in your youth, affecting your speech and shaping your view of the surrounding world.
Born in Osaka (大阪生まれ）, raised in Paris (パリで育てられた）, currently living in Istanbul for work (イースタンブルで済む）. That person's 出身地（しゅっしんち）would be Paris.
In a simple conversational context, asking someone's 出身地 is simply asking where someone is 'from'.