Simplify the following text for a Grade 5 native English-speaking person.
Original: However , by a special act of Congress sponsored by Senator Carl Levin ( D-MI ) that passed on December 28 , 2005 , which President George W. Bush signed on December 31 , 2005 , Belbin became a naturalized citizen , making her able to compete for the United States at the 2006 Winter Olympics .
Simplified: Belbin was sworn in as an American citizen on December 31 , 2005 .