Of the fully human regulars ...
Earth: Picard, Riker, LaForge
Colonies: Crusher, Yar
Earth: Sisko, O'Brien, Bashir
Earth: Janeway, Paris, Kim
Colonies: Chakotay, Seven of Nine
So among the 24th-century humans, that's nine from earth, four from colonies. Not all that surprising given how small most of the colonies we see are.
The more surprising thing is that there is, as far as we're shown, only one Starfleet Academy. Even the modern-day U.S., with a much smaller area and much smaller population, has military training facilities scattered all over the country. Training for officers is more centralized ... until, of course, you start thinking about all the colleges with ROTC programs.