I was curious, so I went back and looked at MNC-winning QBs since 1990 (African-American QBs in bold. /no racist). Split is nearly even. I was also surprised that only four QBs won the Heisman and a MNC the same season; thought that number would have been higher.
1990: Shawn Jones & Mark Brunell
1991: Gino Torretta
1992: Jay Barker
1993: Charlie Ward (Heisman)
1994: Tommy Frazier
1995: Tommy Frazier
1996: Danny Wuerffel (Heisman)
1997: Scott Frost & Brian Griese
1998: Tee Martin
1999: Chris Weinke
2000: Josh Heupel
2001: Ken Dorsey
2002: Craig Krenzel
2003: Matt Mauck & Matt Leinart
2004: Matt Leinart (Heisman)
2005: Vince Young
2006: Chris Leak
2007: Matt Flynn
2008: Tim Tebow
2009: Greg McElroy
2010: Cam Newton (Heisman)
2011: AJ McCarron
2012: AJ McCarron
2013: Jameis Winston (Heisman)
2014: Cardale Jones/JT Barrett (Barrett started 12 regular season games; Jones the B1G title and CFP games)
2015: Jake Coker
2016: Deshaun Watson
2017: Jalen Hurts/Tua (for 1 half of the title game)
2018: Trevor Lawrence
What does that all mean? Not much. Teams can win with a white QB, teams can win with a black QB. What really helps, though, is to have great skill position talent and a good/great defense around the QB.