[PVTree]

For these Olympic qualifying games, it was up to the teams, where the players play, to grant permission for the players to join the national team. When they are "FIFA dates", the teams have to let the players join their national teams if called. 

My understanding is that no team granted the US players in Europe permission to participate in the Olympic qualifiers. Pulisic and others joined the senior team for the friendlies because they are FIFA dates.

[PVTree]

For these Olympic qualifying games, it was up to the teams, where the players play, to grant permission for the players to join the national team. When they are "FIFA dates", the teams have to let the players join their national teams if called. 

My understanding is that no team granted the US players in Europe permission to participate in the Olympic qualifiers. Pulisic and others joined the senior team for the friendlies because they are FIFA dates.