By Nandita Bose PHILADELPHIA (Reuters) -U.S. President Joe Biden blasted Wall Street and Republicans, while making a full-throated defense of his economic plans to thousands of union members in Philadelphia on Tuesday, as he seeks to improve dismal approval ratings amid high inflation and fears of recession. Often raising his voice to a yell, Biden vowed to continue to pursue billionaires and corporations that his administration says underpay billions of dollars in taxes each year, and to pursue economic policies aimed at shrinking U.S. inequality. “Our work isn’t done,” Biden said. “America s…