OMG ... your career's on the verge after Burlesque flops and after Lady Gaga marches straight into your spotlight and still you can't even get the lyrics to our own country's national anthem right during the most-watched TV event of the year, Christina???

Ms. Aguilera flubbed the lyrics to the Star Spangled Banner this evening during the Super Bowl in Dallas, as the Green Bay Packers and the Steelers watched on -- faces looking confused when they heard Xtina sing, "what so proudly we watched" instead of "o'er the ramparts we watched."

Well at least it wasn't as bad as Rosanne Barr's rendition ... But did Lea Michele's America the Beautiful kick Xtina's ...???

Uh, oops!