GM does have a sleeper hot hatch in the US, it's the old Spark EV with 400lb-ft tq. Keep in mind thats an electric motor, full torque instantly. They offer a few lightweight fwd gas hot hatches in Europe. They're mainly Opel OPC's. Vauxhall slaps the VXR badge on as a rebrand. Maybe there's more to it than that.
I think GM is following the lead of what works for Toyota small cars. Ford, Hyundai, Honda, Subaru, Mazda, and others have small sports cars but seem to be lower volume vs Toyota or even Nissan in the Versa. So one idea is brand identity should promote the widest appeal to the avg buyer and the enthusiasts or hotrodders be damned. Bland, sameness, and 'nice looking' are what GM wants for their new small cars, and any hot hatch will be an accidental sleeper, not on purpose. Like the Buick Verano 2.0T - a Cruze SS in disguise.