As everyone else has posted...some of the D pier is in the non-schengen zone and some is in the schengen-zone.
PRG is a non-schengen zone flight so you will not traverse passport control in AMS from the US to Prague and vice versa.
Remember, however, that all US-bound flights have extra security screening at the gate. You will not want to dilly-dally around duty free shops at AMS when you get off the PRG flight. By the time you get to the gate for your US flight, they will have already boarded half the plane and the other half will probably be waiting to get screened.
-RM