As of my knowledge cutoff in September 2021, the most expensive cars available for sale in the USA, along with their prices, were:
Bugatti Chiron Super Sport 300+: Priced at around $5.2 million, this hypercar features a quad-turbocharged 8.0-liter W16 engine that generates 1,577 horsepower and has a top speed of over 300 mph.
Pagani Huayra Roadster BC: With a price tag of around $3.5 million, this Italian supercar is powered by a twin-turbocharged 6.0-liter V12 engine that produces 791 horsepower and has a top speed of over 200 mph.
Bugatti Divo: Priced at around $5.8 million, this limited-edition hypercar is powered by the same quad-turbocharged 8.0-liter W16 engine as the Chiron Super Sport 300+ but has been tuned to produce 1,479 horsepower. Only 40 units of this car will be produced.
Koenigsegg Jesko: This Swedish hypercar is priced at around $3 million and features a twin-turbocharged 5.0-liter V8 engine that produces up to 1,600 horsepower and has a top speed of over 300 mph. Only 125 units of this car will be produced.
Mercedes-AMG One: Priced at around $2.8 million, this limited-edition supercar is powered by a hybrid powertrain that combines a turbocharged 1.6-liter V6 engine from Mercedes-AMG’s Formula One racing program with four electric motors. The system produces over 1,000 horsepower and has a top speed of over 217 mph. Only 275 units of this car will be produced.
It’s worth noting that the prices of these cars may have changed since my knowledge cutoff date and there may be other cars that have been released or announced since then that are more expensive.