EU是哪个国家的简称?

不是国家
是欧盟

EU的全称是European Union,是欧洲联盟的意思,所以不是一个国家的简称,而是一个非政府机构的简称

an international organization of European countries formed after World War II to reduce trade barriers and increase cooperation among its members, 这就是EU(欧盟)的英文解释

European Union