There exists only one SKU for Switch games. The SKU is universal, as it covers all regions at once. There technically is no American copy of Breath of the Wild, just the same as no European or Japanese copy exists. This is because of the Switch being openly region free and all regions sharing the same version of the game between all regions.
I agree that Animal Crossing on the Switch will only have one SKU, but is this universally true? Aren't there certain Switch games, that have multiple versions due to censorship? Wolfenstein in Germany comes to my mind.