RTT NewsFebruary 13, 2011 Regulators announced the closure of four more banks on Friday, taking the U.S. bank failure toll in 2011 to 18. The four banks are in California, Wisconsin, Michigan and Florida. The Federal Deposit Insurance Corp. or FDIC said it closed the Canyon National Bank in Palm Springs, California. To protect the depositors, the FDIC entered into an agreement with California-ba…