There's no single, readily available figure for the total number of cars *produced* in the US in the year 2000. Data on vehicle production usually comes from sources like the US Department of Transportation's National Highway Traffic Safety Administration (NHTSA) or the Bureau of Economic Analysis (BEA), but they often categorize by type of vehicle (cars, light trucks, etc.) and don't always present a simple "total cars produced" number for a specific year.
To get a close approximation, you would need to consult detailed industry reports from that period, which may require archival research.
