Besides Reyna, Emmanuel Sabbi and Henry Wingo scored in Denmark and Norway, respectively, and Joe Efford added another assist for Belgian club Waasland-Beveren.
Besides McKennie, Reggie Cannon debuted for Boavista in Portugal and Eric Lichaj came on in the second half for promoted Turkish club Fatih Karagümrük, which rallied foe a 2-2 tie at Gaziantep.
Youth. Reyna was the youngest American to play this weekend in 13 major European leagues. He was one of 13 Olympic-eligible players who played.
Europe. Seven players who will be playing in the UEFA Champions League or Europa League group stage this fall played this weekend.
UCL=UEFA Champions League.
UCLQ=UEFA Champions League qualifying.
UELQ=UEFA Champions League qualifying.
Erik Palmer-Brown (23), Austria Wien, 90 minutes (2-1 vs. Reid)
Belgium (Pro League)
Joe Efford (24), Waasland-Beveren, 90 minutes, 1 assist (2-4 at Waasland-Beveren)
Ethan Horvath (25), Club Brugge (UCL), on bench (6-0 at Zuite Waregem)
Monday: Chris Durkin, St. Truiden, at Cercle Brugge.
Emmanuel Sabbi (22), OB, 89 minutes, 1 goal (1-1 vs. Nordsjælland)
Haji Wright (22), SönderjyskE (UELQ), sub-15 minutes (1-4 at Vejle)
Monday: Michael Lansing, Horsens, at AaB.
England (Premier League)
Tim Ream (32), Fulham, on bench (3-4 at Leeds United)
Monday: Zack Steffen, Man. City (UCL), at Wolves.
France (Ligue 1)
Tim Weah (20), Lille, sub-13 minutes (1-1 at Marseille)
Tyler Adams (21), RB Leipzig (UCL), 90 minutes (3-1 vs. Mainz)
John Brooks (27), Wolfsburg (UEL), 90 minutes (0-0 vs. Bayer Leverkusen)
Tim Chandler (30), Eintracht Frankfurt, sub-3 minutes (1-1 vs. Arminia Bielefeld)
Gio Reyna (17), Borussia Dortmund (UCL), 77 minutes, 1 goal (3-0 vs. Bor. Dortmund)
Chris Richards (20), Bayern Munich (UCL), sub-18 minutes (8-0 vs. Schalke 04)
Josh Sargent (20), Werder Bremen, 90 minutes (1-4 vs. Hertha Berlin)
Italy (Serie A)
Weston McKennie (22), Juventus (UCL), 90 minutes (3-0 vs. Sampdoria)
Luca de la Torre (22), Heracles, 57 minutes (0-4 at Willem II)
Sergino Dest (19), Ajax (UCL), sub-12 minutes (3-0 vs. RKC Waalwijk)
Devesio Payne (24), Emmen, sub-2 minutes (1-2 at PSV)
Henry Wingo (24), Molde (UCLQ), 40 minutes 1 goal (1-2 at Valerengen)
Portugal (Primeira Liga)
Reggie Cannon (22), Boavista, 90 minutes (3-3 at Nacional)
Scotland (Premier League)
Ian Harkes (25), Dundee United, 90 minutes (2-1 vs. St. Mirren)
Aron Johannsson (29), Hammarby, 90 minutes (0-3 at AIK)
Nebiyou Perry (20), Ostersunds FK, 70 minutes (1-1 at Djurgarden)
Monday: Mix Diskerud, Helsingborg, at Varberg, Romain Gall, Jake McGuire, both Orebro, at Mjallby.
Tyler Boyd (25), Besiktas (UELQ), 90 minutes (1-1 at Antalyaspor)
Eric Lichaj (31), Fatih Karagümrük, sub-30 minutes (2-2 at Gaziantep)