By David French and Megan Davies NEW YORK (Reuters) – Western sanctions on Moscow could throw the small but lucrative Russian investment banking business that several large U.S. banks have maintained into question, lawyers said, which could deal a hit to tens of millions of dollars in fees. Major U.S. banks, including JPMorgan Chase & Co, Morgan Stanley and Citigroup Inc, have continued to underwrite and advise on Russian deals, often alongside the investment banking arm of state-owned VTB. VTB Capital is the largest investment bank by fees in Russia. But U.S. sanctions placed on Thursday on V…