HOBOKEN, N.J.—As a player from Barcelona closed down on him, Mark Cajamarca touched the ball to the side, creating some space for himself before sending a pass to an oncoming teammate. It was a subtle move for the 12-year-old, already a star in the New York City FC academy system, and showed the type of soccer acumen that had international coaches talking all weekend in north Jersey about the potential of American players.



This year’s La Liga Promises tournament returned to the New York City area on the second Friday in June. The venue was Hoboken’s Frank Sinatra Park, which featured a sun-splashed view of Manhattan as top U-12 teams from Barcelona, Real Madrid, Valencia, and other Spanish clubs competed against local youth teams, including the New York Red Bulls and NYCFC. Last year, NYCFC didn’t advance out of the group stage. This year, the club secured a scoreless draw against Barcelona and made it to the quarterfinals.



In other words, the...