Why is it en France, en Espagne, en Italie but AU Japan? S'il vous plait

Because you use "en" with feminine countries and "au" with masculine countries. I had learned in high school French that you use "au" with the state I live in, Texas. Most countries that end in "e" are feminine, but there are exceptions such as Mexique, Belize, Mozambique, Cambodge which are all masculine.