Nascar has long held a rule that only American-made cars or trucks may compete in its events.
About 4,000 American-made cars were imported by Japan last year.
The companies said 266,492 American-made cars and light trucks had been sold in the latest period.
Sales of American-made cars and light trucks rose 2.9 percent in late March.
"It'll still be an American-made car - with some foreign ideas."
Typically, they tend to be based on American-made cars from the 1930s and 1940s.
In future, I will avoid American-made cars, no matter how attractive they appear.
Sales of American-made cars and light trucks dropped 3.6 percent in late May.
To be sure, front-wheel drive is likely to remain in the majority of American-made cars.
The price of American-made cars rose an average of 25 percent during the same period, to $14,010 in 1988.