Since then, 40 other Americans have played in Europe's top club competition. The list includes Jermaine Jones, Kenny Saief and Malik Tillman, who filed switches of association to represent the USA after their first appearances in the Champions League. It doesn't include players who have appeared in the competition's preliminary stage.
European Cup:
1990-91
1. Steve Trittschuh (Sparta Prague, Czechoslovakia, 2 games, 136 minutes
1991-92
2. Thomas Dooley (Kaiserslautern, Germany) 3 games, 270 minutes
UEFA Champions League:
1996-97
3. Jovan Kirovski (Bor. Dortmund, Germany), 2 games, 27 minutes
1997-98
Jovan Kirovski (Bor. Dortmund, Germany), 3 games, 178 minutes, 1 goal
1999-2000
4. Frankie Hejduk (Bayer Leverkusen, Germany), 5 games, 325 minutes
5. Claudio Reyna (Rangers, Scotland), 4 games, 283 minutes
6. Tony Sanneh (Hertha Berlin, Germany), 6 games, 263 minutes, 1 assist
2000-01
Claudio Reyna (Rangers, Scotland), 4 games, 356 minutes
Frankie Hejduk (Bayer Leverkusen, Germany), 1 game, 71 minutes
2002-03
7. John O'Brien (Ajax, Netherlands), 5 games, 449 minutes
2003-04
8. Tim Howard (Man. United, England), 5 games, 450 minutes
2004-05
9. DaMarcus Beasley (PSV, Netherlands), 10 games, 474 minutes, 3 goals
10. Robbie Russell (Rosenborg, Norway), 4 games, 264 minutes
Tim Howard (Man. United, England), 2 games, 180 minutes
11. Jermaine Jones (Bayer Leverkusen, Germany), 2 games, 81 minutes
12. Landon Donovan (Bayer Leverkusen, Germany), 2 games, 76 minutes
13. Jonathan Spector (Man. United, England), 1 game, 22 minutes
2005-06
DaMarcus Beasley (PSV, Netherlands), 5 games, 394 minutes, 1 assist
2006-07
14. Benny Feilhaber (Hamburg, Germany), 3 games, 156 minutes
2007-08
Jermaine Jones (Schalke 04, Germany), 8 games, 725 minutes, 1 goal, 1 assist
DaMarcus Beasley (Rangers, Scotland), 5 games, 247 minutes, 1 goal, 1 assist
15. Freddy Adu (Benfica, Portugal), 2 games, 31 minutes
2009-10
DaMarcus Beasley (Rangers, Scotland), 2 games, 50 minutes
16. Oguchi Onyewu (AC Milan, Italy), 1 game, 30 minutes
2010-11
17. Maurice Edu (Rangers, Scotland), 4 games, 354 minutes, 1 goal
Jermaine Jones (Schalke 04, Germany), 4 games, 239 minutes
2012-13
18. Michael Parkhurst (Nordsjælland, Denmark), 6 games, 540 minutes
Jermaine Jones (Schalke 04, Germany), 6 games, 422 minutes, 1 goal, 1 assist
19. Sacha Kljestan (Anderlecht, Belgium), 5 games, 404 minutes, 2 assists
Oguchi Onyewu (Malaga, Spain), 3 games, 180 minutes
2013-14
Sacha Kljestan (Anderlecht, Belgium), 5 games, 442 minutes, 1 goal, 1 assist
Jermaine Jones (Schalke 04, Germany), 3 games, 251 minutes
20. Julian Green (Bayern Munich, Germany), 1 game, 2 minutes
2014-15
Sacha Kljestan (Anderlecht, Belgium), 4 games, 189 minutes
21. Gedion Zelalem (Arsenal, England), 1 game, 44 minutes
2015-16
22. Fabian Johnson (Bor. M'Gladbach, Germany), 5 games, 424 minutes, 2 goals, 2 assists
23. Kenny Saief (Gent, Belgium), 7 games, 355 minutes, 1 assist
Julian Green (Bayern Munich, Germany), 1 game, 62 minutes
2016-17
24. Christian Pulisic (Bor, Dortmund, Germany), 10 games, 598 minutes, 1 goal, 2 assists
Fabian Johnson (Bor. M'Gladbach, Germany), 5 games, 343 minutes
2017-18
Christian Pulisic (Bor. Dortmund, Germany), 5 games, 374 minutes
2018-19
Christian Pulisic (Bor. Dortmund, Germany), 7 games, 453 minutes, 1 goal
25. Weston McKennie (Schalke 04, Germany), 6 games, 373 minutes, 1 goal
26. Ethan Horvath (Club Brugge, Belgium), 3 games, 270 minutes
2019-20
27. Sergino Dest (Ajax, Netherlands), 5 games, 405 minutes
Christian Pulisic (Chelsea, England), 4 games, 266 minutes, 1 goal, 1 assist
28. Tyler Adams (RB Leipzig, Germany), 3 games, 82 minutes, 1 goal
29. Gio Reyna (Bor. Dortmund, Germany), 2 games, 43 minutes, 1 assist
2020-21
Sergino Dest (Barcelona, Spain), 7 games, 585 minutes, 1 goal
Gio Reyna (Bor. Dortmund, Germany), 8 games, 458 minutes, 1 assist
Christian Pulisic (Chelsea, England), 10 games, 423 minutes, 2 goals, 2 assists
Weston McKennie (Juventus, Italy), 7 games, 403 minutes, 1 goal
Tyler Adams (RB Leipzig, Germany), 6 games, 289 minutes
30. Chris Richards (Bayern Munich, Germany), 3 games, 129 minutes
Ethan Horvath (Club Brugge, Belgium), 1 game, 90 minutes
31. Zack Steffen (Man. City, England), 1 game, 90 minutes
32. Konrad de la Fuente (Barcelona, Spain), 2 games, 19 minutes
2021-22
33. Brenden Aaronson (Red Bull Salzburg, Austria), 8 games, 714 minutes, 2 assists
Weston McKennie (Juventus, Italy), 6 games, 389 minutes
Christian Pulisic (Chelsea, England), 7 games, 366 minutes, 2 goals, 1 assist
34. Jordan Pefok (Young Boys, Switzerland), 6 games, 339 minutes, 2 goals
35. John Brooks (Wolfsburg, Germany), 4 games, 329 minutes
Tyler Adams (RB Leipzig, Germany), 5 games, 292 minutes
36. Timothy Weah (Lille, France), 5 games, 254 minutes
Sergino Dest (Barcelona, Spain), 4 games, 230 minutes
Zack Steffen (Man. City, England), 1 game, 90 minutes
37. Malik Tillman (Bayern Munich, Germany), 2 games, 20 minutes
2022-23
38. Josh Cohen (Maccabi Haifa, Israel), 6 games, 540 minutes
Gio Reyna (Bor. Dortmund, Germany), 6 games, 382 minutes, 2 assists
39. Cameron Carter-Vickers (Celtic, Scotland), 4 games, 360 minutes
Weston McKennie (Juventus, Italy), 5 games, 359 minutes, 2 goals
40. James Sands (Rangers, Scotland), 4 games, 324 minutes
Malik Tillman (Rangers, Scotland), 5 games, 244 minutes
Sergino Dest (AC Milan, Italy), 4 games, 188 minutes
Christian Pulisic (Chelsea, England), 5 games, 111 minutes, 1 assist
41. Tim Chandler (Ein. Frankfurt, Germany), 1 game, 12 minutes
Source: fbref.com