In 1976, Tamraz moved into United States financial markets with his acquisition of Bank of the Commonwealth, a Michigan-based bank with 50 branches. He strengthened and expanded the bank until 1983, when it was merged into the founding of Comerica, Inc., now one of the largest super-regional U.S. bank holding companies. The merger made Tamraz the largest single shareholder in Comerica at the time, before selling out to finance the Tamoil acquisition described below.