The original Vocaloid software only came with a english interfacem even for Japanese vocaloids like Meiko and Kaito. Vocaloid 2 had access to Japanese and English languages though only sold with the engine version for that language (Luka being made for Japanese only had a Japanese engine despite having a English voicebank as well as a Japanese one). vocaloid 3 i localised so it can install in all languages its intend for; English, Japanese, Korean, Spanish and Chinese.
So yeah, it will work on an american computer,
Do note, no matter what a Japanese vocaloid will only have access to Japanese phonetic data, ditto for Korean, Spanish and English vocaloid have only access to their respectve language data.