[5] Three additional characters, consisting of Dewey, Louie, and Ludwig Von Drake, can be unlocked in the N64 version through completing objectives in Grand Prix mode; a fourth character, Huey, can only be unlocked by connecting to the GBC version through the Transfer Pak.

Professor Ludwig von Drake builds race cars for the group to help them search faster, and they travel across America following a series of postcards left by the Weasels.

Mickey happily reunites with Pluto, revealing the supposed diamonds on his collar are simply glass beads from one of Minnie's old necklaces, and the group heads home.

[25] Matthew Byrd, writing for Den of Geek in 2017, said that Mickey's Speedway USA could not compete to other similar titles like Diddy Kong Racing, Mario Kart 64, or Crash Team Racing, due to its courses being not nearly as "inventive" (only a basic recreations of US locations), its power-ups as "little slim", its "problematic" artificial intelligence, and its roster of karts and tracks as "thin".

Despite its flaws, he thought that Rare managed to produce an engagingly charming and functional kart racing title.