The title pretty much states my question. I know there have been many many MLS players that played for their country in the World Cup while they were on MLS rosters but I cannot remember any MLS players that were on a World Cup winning team while they were in the MLS.
I doubt it. 2014 - Germany, nope. Four EPL, two Serie A, the rest in the Bundesliga 2010 - Spain, nope. Three EPL, the rest La Liga 2006 - Germany, nope. Two guys in the EPL, the rest in the Bundesliga 2002 - Brazil, nope. Mostly in Brazil but a few in Italy, Spain, France, and Germany 1998 - France, nope. Mostly playing in France and Italy. 3 EPL, 1 Spain, and 1 Germany.
Has MLS ever had a player reach the Semifinals? Obviously the Quarterfinals in 2002 was the best the USMNT did since MLS started.
Last time Julio Cesar went on loan to TFC to get playing time leading up to the World Cup. Not sure if that "really counts" though even though his loan didn't expire until after the World Cup.
Toronto FC was his most recent club before World Cup 2014 and is his club at https://www.fifadata.com/document/FWC/2014/pdf/FWC_2014_SquadLists.pdf so he counts.
Post 2,196 of https://www.bigsoccer.com/threads/random-world-cup-facts.212289/page-88 says 10 World Cup winners have played in MLS at some point, but none were in MLS before they won the World Cup: Branco (won in 1994, MetroStars 1997) Denilson (won in 2002, FC Dallas 2007) Djorkaeff (won in 1998, Red Bulls 2005-2006) Henry (won in 1998, Red Bulls 2010-2014) Kaka (won in 2002, Orlando City 2014-2017) Kleberson (won in 2002, Philadelphia 2013) Nesta (won in 2006, Montreal 2012-2013, only World Cup winner to play for a Canadian MLS club) Pirlo (won in 2006, NYCFC 2015-2017) Schweinstieger (won in 2014, Chicago 2017-now) Villa (won in 2010, NYCFC 2014-2018) The Red Bulls/MetroStars with 3 and NYCFC with 2 are the only clubs with more than 1. Djorkaeff and Henry are the only World Cup winning teammates to play for the same MLS club (not at the same time). Pirlo and Villa are the only World Cup winners to be MLS teammates. I didn't see Branco on the MetroStars 1997 statistics page, and I discovered that his name is Claudio Vaz Leal. He played in 11 MLS games.