C data by YCharts NEW YORK (TheStreet) -- Citigroupa ,aBank of Americaa and JPMorgan Chasea are finally showing signs of life. The three largest U.S. banks have lagged the S&P 500 asince late-2009 when this current bull market took hold. But that's beginning to change. Bank stock over the past four weeks are showing strength, prompted in part by U.S.