He will report directly to Euro RSCG Chicago's president and chief executive, Ron Bess.
Bess said: "John's combined knowledge of agency leadership, account management and business development make him a perfect fit for this new position."
Minnec will also take some of the management responsibilities previously held by Zain Raj, recently promoted to chief executive of Euro RSCG Discovery.
While president at DraftFCB London, Minnec was responsible for overall operations and client services.
He also led the agency's business development team, helping to win six new accounts, and was responsible for various global accounts including Nokia.
As well as more than 11 years at Draft, his career has included working at Ogilvy & Mather, Grey and Leo Burnett. He was also the president of his own boutique agency, Moesch and Minnec, from 1990 to 1993.
Minnec is a recognised speaker on global marketing, and was a keynote speaker at the International Advertising Association's forum in China 2005.