Most crucially, it never left Japan. The text-based nature of the game—letters, conversations, and the entire "crankigai" (turnip) economy—made a simple port without heavy localization impossible. So, Nintendo of America and Nintendo of Europe did what they often did in that era: they waited. They commissioned a full, ground-up localization for the more powerful GameCube, adding holidays, new items, and an island. The N64 original was left behind, a relic locked behind a language barrier.
Furthermore, the ROM itself was a moving target. Dumping a clean, working N64 ROM is one thing; inserting English text into a game engine never designed for variable-width fonts is another. The N64's text-rendering system expected fixed-width Japanese characters. Early patches resulted in text that spilled off the screen or corrupted save files. animal crossing n64 rom english