MEXICO CITY - If Arnold Schwarzenegger had migrated to Mexico instead of the United States, he couldn't be a governor. If Argentina native Sergio Villanueva, firefighter hero of the Sept. 11 attacks, had moved to Tecate instead of New York, he wouldn't have been allowed on the force. Even as Mexico presses the United States to grant unrestricted citizenship to millions of undocumented Mexican migrants, its officials at times calling U.S. policies "xenophobic," Mexico places daunting limitations on anyone born outside its territory. In the United States, only two posts — the presidency and vice presidency — are reserved for...
