The Argentine parted ways with the Premier League club on Sunday and was quickly replaced by the American.
It followed a dismal run of results that has seen them dragged into the relegation battle with their top flight status seriously under threat.
Bielsa reportedly said an emotional goodbye to the Leeds and there were plenty of tears.
He will forever be regarded as a hero for the club after getting them promoted back into the Premier League after a 16-year exile.
Now it is up to American Marsch to keep them up with 12 games left to go.
The 48-year-old's experience has come as assistant with the United States national side, before spells as manager of Montreal Impact, New York Red Bulls, Red Bull Salzburg and RB Leipzig.
Former Charlton, Tottenham and Sunderland striker Darren Bent believes it is a huge risk appointing someone with now previous Premier League experience.
He said: "I give them as much hope as I did when Bielsa was in charge. He's ingrained in them the style of football he played, which is going to take a long time to change.
"Look at Crystal Palace under Roy Hodgson, they were used to playing the same way and even though we all probably agree that watching Palace this season under Patrick Vieira has been better, they are not any better off points-wise than last season.
"I think it's a risk. If they are going for someone with Premier League experience, has been a top coach and has the pedigree to come into the toughest league in the world and change things around when a team is in free fall, a bit like Roy Hodgson at Watford, then you will go 'okay'.
"He's managed in the MLS, the Austrian Bundesliga, so it is a risk. These aren't big, big domestic leagues and not the powerhouses of world football.
"It's going to be interesting but I think the hangover will be there for some time."