How many college football stadiums in the USA are built below ground level?

Ben Hill Griffin Stadium, University of Florida. Originally built in a ravine, the playing surface is below ground level.

http://www.americasbestonline.com/cstadiums.htm

University Stadium is an outdoor football stadium on the south campus of the University of New Mexico in Albuquerque, New Mexico. The stadium was built in an existing arroyo with the grandstands built up from moved earth for an earthen fill that was then cemented over. This "berm" style construction placed the field below ground level with seats above and below the natural ground level.

https://en.wikipedia.org/wiki/University_Stadium_(Albuquerque)

Stanford Stadium

The current Stanford Stadium occupies 18.4 acres (74,000 m2), with a footprint of 601,128 sq ft (55,846.6 m2)., a playing surface 29 feet (8.8 m) below ground level,

https://en.wikipedia.org/wiki/Stanford_Stadium

Rice Stadium at Rice University campus in Houston, Texas.

The entire lower seating bowl is located below the surrounding ground level. Built solely for football, the stadium has excellent sightlines from almost every seat.

https://en.wikipedia.org/wiki/Rice_Stadium_(Rice_University)