Guesses - since the letter arrived...

Sarah - midwest US
Kristen - Compton. (so he can be among his people)
Matthew - Japan
Anthony - Yugoslavia
Mom - Canada or Fernley
Dad - New Zealand, my alma mater
Ashley - South Dakota - since his mission covers a corner of the state, we shall declare Ashley the winner...here is your prize...um, somewhere, I know I had one...oh, well, better luck next time.
Grandma - Australia
Jonathon -
Mike -
Tim -
Aunt Karin -
Elizabeth - Canada
Diana - New York/Canada
Brinae - Australia
Leslie - Romania
Jared - Australia
Alyea - New Zealand
Andy - Brazil, Florida
David - Wisconsin
Alysse - Spain
Langley - Alaska
Kathryn - Texas
Jonny - Billings, Montana
Talia - Moscow
Jenny - Lima, Peru