Nippon Steel Corp. said Wednesday the majority of board members and core senior management of United States Steel Corp. would be U.S. citizens if its acquisition by the Japanese firm goes ahead. Japan’s largest steelmaker made the announcement days after U.S. Vice President Kamala Harris voiced opposition to the buyout, saying it should be run domestically. The deal has yet to win approval from U.S. regulators. Nippon Steel, which has already said U.S. Steel will remain headquartered in Pittsburgh, said in a press release that the post-acquisition board would also include three independent dir…