If you found this file as part of a larger collection, it is likely just the standalone American version of the game. if the dump is "clean"? ROM Naming Conventions - General Discussion - EmuMovies

Mario Kart 64's gameplay mechanics have stood the test of time. The game's controls are still tight and responsive, making it a joy to play even today. The game features a variety of modes, including:

: The game featured eight characters. Wario made his debut, and Donkey Kong replaced Donkey Kong Jr. from the original SNES game. Legacy and Impact Mario Kart 64 sold 9.87 million copies

If you have a .v64 file, the bytes are essentially "backwards" compared to how the N64 CPU naturally reads them. While almost all modern emulators (like Project64, RetroArch, or Mupen64Plus) can handle both formats automatically, archivists prefer .z64 because it is an exact, unswapped copy of the cartridge data.

And the -u- ? It doesn’t stand for United States anymore. It stands for unsolved .