Petersen has lived in the United States for more than a decade, married U.S. rider and trainer Melissa Taylor in 2013, and has been a U.S. citizen since February 2016.
For Petersen it was the "right time", to make the switch. According to the FEI rules there is a mandatory two-year gap between when a rider competed for a previous country at a major championship or on a CDIO Nations Cup and when the rider can compete for a new country at those competitions.
Petersen has ridden for Denmark at Olympic Games, World Cup Finals and the 2014 Alltech FEI World Equestrian Games (France), and he’s aiming to work his way back to international competition. He will retain his dual Danish citizenship.