Allstate Corp has sued Bank of America Corp and 18 other defendants over losses it said it suffered on more than $700 million of mortgage debt it bought from Countrywide Financial Corp. In a complaint filed Monday in Manhattan federal court, Allstate, the largest publicly traded U.S. home and auto insurer, alleged that Countrywide misled it into believing the securities it bought were safe, and that the quality of residential home loans backing them was high.