Complex sentence: Upon her return to the United States, she served as Director of the Office of Russian Affairs at the State Department from 2004-2007 and in August 2007 was appointed Special Assistant to President George W. Bush and Senior Director for Russia at National Security Council.
Split into simpler sentences: Upon her return to the United States, she was appointed Director of the Office of Russian Affairs at the State Department. She held the position until August 2007, when she was appointed Special Assistant to President George W. Bush and Sr. Director for Russia at National Security Council.