Bimmerfile just published an interview (provided by BMWNA) with Larry Koch, M Brand Manager of BMW NA, on the GTS:
Q: “Why won’t BMW NA bring the M3 GTS to the United States?”
LK: When I first started discussing the GTS with M in Garching [Munich], I knew it could be a hit in the US, albeit most likely a short-lived hit given such a high price [110,000 Euros before US homologation]. However, when taking a closer look, we realized the car does not pass any EPA or federal safety standards. Those are two big catches for importing a new BMW, even in small volumes. Modifying the GTS to make it US-compliant would be a very costly affair because the car lacks airbags, proper DOT seatbelts, proper bumper height, etc. And those are just the safety items. Keep in mind the 4.4 liter engine is not homologated for the US which would require more than a simple set of racing catalysts [as the car is currently equipped]. Rest HERE.
Like assumed earlier, the necessity for US homologation prevented BMW from offering the GTS in the USA. Furthemore, Larry Koch mentions the Competition Package. Most interesting seems to be that he mentions the revised MDM mode in case ZTP is ordered.
Make sure to visit bimmerfile to read the full interview.