The FDIC, a U.S. bank regulator, has sued three large U.S. banks to recoup some of the more than $695 million it lost from selling shoddy residential mortgage-backed securities once owned by a Texas bank that failed in 2009. Lawsuits stemming from the FDIC’s role as receiver for Austin-based Guaranty Bank, which had bought more than $2.7 billion of the securities, were filed against Citigroup Inc , Bank of New York Mellon Corp and US Bancorp late Wednesday in Manhattan federal court.