Critics and bloggers flocked online to point out Christina Aguilera's blunder, while footage of the mistake has already became a popular video on clip-sharing website YouTube.com.
Now the singer has apologised for the incident, releasing a statement which reads: "I got so caught up in the moment of the song that I lost my place. I can only hope that everyone could feel my love for this country and that the true spirit of its anthem still came through."
Meanwhile, a number of Christina Aguilera's celebrity fans have taken to Twitter.com to congratulate her on a job well done.
Fellow Super Bowl performer will.i.am, who provided the half-time entertainment with his Black Eyed Peas bandmates, shared a photo of the star performing and tweeted: "Xtina sing'n wonderful."
Singer Natasha Bedingfield wrote, "She did great! She sung her heart out. Didn't you see one of the players was so moved he was crying?! I'd like to see you try and do that!", while Pussycat Dolls star Nicole Scherzinger, who was in the crowd at the Arlington, Texas event, declared: "Xtina (Christina) just killed it 'sangin'! Sounded amazing here."
Singer Jordin Sparks added: "The test of a true artist is continuing even when things go a little left & not letting people know it did during the performance. I love Xtina."