US manager Jurgen Klinsmann provided his rationale to FOX, which carried the official unveiling of the squad at halftime of Saturday's New York City FC vs. New York Red Bulls match.
"There are always some 50-50 moments, if it's in the back line, if it's in midfield, if it's up front," Klinsmann told FOX. "And it came a little bit down to Wondo [Chris Wondolowski] or Jordan.
"We decided in this moment right now to go with Wondo. He's in top form. He's scoring a lot of goals for the Earthquakes. But always, when you take certain players in one area, you have to leave other ones out."
The 33-year-old Wondolowski, who extended his contract with San Jose on Friday, has seven goals and two assists with the Earthquakes so far this year. His seven goals came in seven different matches.
For his part, the 21-year-old Morris has four goals and one assist in his rookie season in MLS, with all four goals coming in a four-game stretch between April 16 and May 7, tying the record for consecutive matches with a goal by an MLS rookie. Klinsmann gave Morris his USMNT debut while he was still in college with Stanford, and he had a total of seven senior caps before he signed with the Sounders in January 2016.
"We believe that players really played their way into that [Copa America] roster, and it’s difficult," Klinsmann said in a quote sheet provided by US Soccer. "There are some situations that probably the fans will now discuss. Why not Jordan Morris and Wondo is in there? Well, because Wondo proves all the time that he just is so hungry for goals, and Jordan is on his way through the ranks coming up."