Neither should or will be starting. Let's not mistake some nice run out in some friendlies with taking on some elite squads. Pulisic is 17. Nagbe has been less than stellar with his MLS team this season. Both of their times will come, but neither are the current answer to what ails the US. Pulisic's abilities to maintain possession may see him getting time when the US are needing control of a game. Nagbe will come on when whatever slow US attacker has finally exhausted their usage. Either way, Klinsmann's job will not be determined by those two. The player who could really help the US attack here is Bobby Wood. If he continues to let Dempsey, Jones, Zardes try and control play they will be overwhelmed.
US has drawn Colombia, Costa Rica and Paraguay. There is a significant chance they do not emerge from their group.