I got mail from Nick regarding this championship as below
Team qualifying:
U.S. Puzzle Championship - Saturday, Sept. 5
Sudoku Team Qualifying Test - Sunday, Sept. 6

Please visit the USA website for further details:
U.S. Puzzle Championship: http://wpc.puzzles.com/uspc2015 (update Aug 31)
Sudoku Team Qualifying: http://wpc.puzzles.com/ussq2015 (update Aug 31)