First this is not a knock on the guy or Americans not born here - but to be the greatest American Distance Runner I think you should only include what was done while American... So for sure Lagat belongs as would Chelimo or Lomong if they are deemed to be in the mix but I vote against Khannouchi being in this list
He became a Naturalized citizen in May of 2000 His resume from that point on is as follows:
2000
Chicago Marathon, winner in a new American record (2:07:01)
2002
London Marathon, winner in world record time (2:05:38)
Chicago Marathon, winner (2:05:56), becoming the first man in history to break 2:06 twice in one year
Ranked as the number #1 marathoner in the world by Track & Field News and their American Athlete of the Year.
2004
Chicago Marathon, fifth place (2:08:44)
2006
London Marathon, 4th place (2:07:04), coming back from a long period of injury.
2007
London Marathon, did not finish.
United States Olympic Marathon Trials in New York City, 4th place (2:12:34)[1]
SO an amazing and epic 2002 - but is that enough?