2016 Cadillac CTS-V First Drive - 640 all-American horses

There's a moment, just after you start up the 2016 Cadillac CTS-V, when the seat belt gently contracts around you, almost like the 640 horsepower super-sedan is giving you a hug. It's a reassuring gesture, though a little at odds with the near-simultaneous gurgle from the engine as the exhaust valves flutter. "Sure, I'm 16.5 feet long, weigh more than …