Your USB HDD may be too slow. Brawl streams data constantly. Use a USB 2.0 flash drive (64GB max) or a mechanical hard drive with external power. Avoid cheap, no-name flash drives.
While there is no official Nintendo release titled "Super Smash Bros. Brawl Universe," "Universe" is a well-known of the base Super Smash Bros. Brawl game. Mods like these are typically distributed in the WBFS format for use on homebrew-enabled Wii consoles or emulators. super smash bros brawl universe wbfs
Custom "Universe" builds often have high-resolution textures. Using a high-speed USB 3.0 drive (even though the Wii uses 2.0) can help stabilize data transfer rates. Conclusion Your USB HDD may be too slow
Super Smash Bros. Universe (SSBU) is technically a massive modification (mod) for Super Smash Bros. Brawl super smash bros brawl universe wbfs