While there is some school/league bias in team selection, I think it is more just that those picking teams will lean to players that they have watched a lot. Players on Boston-based rosters have a little bit of an edge in that respect, because anyone scouting the East will be able to see them frequently.
The other factor at play is future versus present. Yes, Worlds is important, but the Olympics are two years away. There may be some motivation to add a player to this roster that has a chance to make an impact in two years, even if they aren't necessarily better than others today.
For example, let's look at only players with Minnesota connections. Jen Schoullis didn't make the cut this time, but I believe she is more of a known quantity. She has shown what she can do at the NCAA tournament and past international events. Meanwhile, Hannah Brandt is still in high school. Do I think she'd be more effective at this month's Worlds than would Schoullis (or West or Erickson for that matter)? No. I have a ton of respect for Brandt, but high school is high school, and players develop at a different pace once they get on a college workout program. In two years, however, she will be a far different player, just as Decker or Kessel were much better as college sophomores than they were as prep players. So I think some players are picked based in part on perceived upside. And next time a roster is picked, they might all be left home and someone like an Alex Carpenter could be chosen instead. But I think it is all done with one eye on Sochi.