The 51-year-old coached the All Blacks from late 2001 through to the conclusion of the unsuccessful 2003 World Cup campaign.
Prior to that he was an assistant to England coach Clive Woodward in the late 1990s and was credited with building the England forward pack that won the 2003 World Cup.
In Super Rugby he coached his home town Chiefs and the Western Force, as well as the Lions in South Africa and Sale in England.
The former No 8, who played six games for the All Blacks in 1993, but no tests, replaces Mike Tolkin who led the US at last year's World Cup in which they failed to win a match.
"For me personally, this is a very powerful nation that has an immense audience for this amazing sport," Mitchell said.
"Having worked previously with [USA Rugby chief executive] Nigel Melville, and knowing his level of experience and knowledge in all aspects of the game, I am confident in my decision to take on this role."
Mitchell's first game in charge will be the Eagles Americas Rugby Championship clash against Argentina on February 6 in Houston. He takes the job in a pivotal moment for the game in the US, with its first professional league starting this year.
One of his goals is to widen the player talent pool. He had been impressed with some aspects of the Eagles play at the last World Cup, although felt there was still plenty to work on. They continue to build towards getting more matches against top-tier nations before the 2019 tournament in Japan.
"They struggled to get back on structure and get into shape from chaos," Mitchell said of the Eagles performances in England.
"They often denied themselves opportunities to put pressure on the opposition as a result of this.
"Plenty of good stuff though that will become even better when the players understand their structures and own it."
