Like a Prayer (Madonna with Cee Lo Green)
M.I.A. and Nici Minaj and CeeLo Green and LMFAO
Bill Joel sang the national anthem at Super Bowl XLI (Super Bowl 2007).
Christina Aguilera sang the National Anthem at Super Bowl XLV (45).
Madona
Garth Brooks sang the national anthem at Super Bowl XXVII.
Christina Aguilera sang the national anthem at Super Bowl XLV.
Neil Diamond sang the National Anthem for Super Bowl XXI
Diana Ross was the halftime performer. She was last seen exiting in a helicopter.
yes, Carrie Underwood sang the National Anthem at Super Bowl XLIV.
Lea Michele, or Rachel Berry from Glee, sang "America the Beautiful" at Super Bowl XLV.
The main theme of Madonna promo in 2012 was to advertise the Super Bowl. What this means is she wanted more people to watch it. If someone heard she sang live at the Super Bowl then they would watch next year. Also when they watch they see new commercial they want to buy it. So mostly to advertise is what this answer is about.
The Who