The £50m takeover will erase Derby's debts of around £25 million and provide funds for manager Paul Jewell.
GSE chairman Andy Appleby said: "We are excited about the opportunity to make a significant impact and are impressed with the club's incredible potential."
Appleby is chairman of the Detroit-based GSE, which owns several minor league basketball and ice hockey teams. As former senior vice-president of the Detroit Pistons NBA basketball team, Appleby conforms to the profile of new American investors in English Premier League football clubs.
Adam Pearson, who took over as executive chairman in October will retain his position as chairman, and Appleby will join him on the board.
Tom Glick, a former chief marketing officer for the New Jersey Nets basketball team, is to be brought in as a new president and chief executive.
