The rumors are only partially true. All Toyota Supras are legal in the United States except one model. The NHTSA decided to ban the 1994 model of the Toyota Supra due to chronic reliability issues.
These reliability issues caused a downfall in sales, leading to the eventual U.S. discontinuation of the Supra in 1998. But, Supra enthusiasts will be pleased to hear that the car made a triumphant return to production in 2020.