This could be the summer of IndyCar. Formula One fatigue is beginning to set in , both globally and among the American audiences who helped fuel the sport’s recent boom. Nascar, for all its national reach in the US and lingering cultural import, remains a largely regional attraction. IndyCar, on the other hand, boasts a wealth of personalities, is anchored in real structural parity and delivers wheel-to-wheel action time and again. But as the buildup begins for the 110th running of this year’s Indianapolis 500 – still the sport’s commercial, spiritual centerpiece and Memorial Day weekend staple – IndyCar is at risk of tripping over itself in its rush to return to prominence. As part of its promotional push for the Freedom 250, a Washington DC street race sanctioned by a Donald Trump executive order, IndyCar unveiled a licensed T-shirt that quickly drew attention online, and not just for its $50 price tag.…