LeAnn Rimes showed off her tight stomach in a retro bikini on 'America's Got Talent' Wednesday night. She performed her latest hit, 'Swingin,' and jumped to straddle a backup dancer at one point."Our performance was spot on!" Rimes wrote on her Twitter page on Friday, two days after the performance. "I'm incredibly proud of it!! And performing in a bikini in front of 26 million people keeps you going ;)"
