It sounds as if you want to import a car into the United States so that you can sale the car or transfer ownership to an American here in the US. If this is correct you should check with the National Highway and Traffic Safety Administration (NHTSA) whom gives information regarding importing cars into the US at www.nhtsa.dot.gov/cars/rules/import.
The US has restrictions on the types of vehicles that can be imported, even from Canada, so you want to make certain that the car fits the Federal Vehicle Safety Standard (FMVSS) and will pass EPA emissions tests. There will like be both transfer fees and taxes that you and the American will need to pay either in Canada or the US or both as the car is exported out of Canada and imported into the US.
Contact an agency such as Transport Canada to find out if there are any fees for exporting the vehicle. While regarding expenses from the US side, check with the Customs and Border Patrol, www.cpb.gov.
The American receiving the car should check with their state's Department of Motor Vehicles to find out what paperwork they will need to tile and register the car once the ownership has been transferred.