U.S. President Barack Obama shakes hands with Cuba's President Raul Castro as they hold a bilateral meeting during the Summit of the Americas in Panama City April 11, 2015. (Jonathan Ernst/Reuters) The face-to-face conversation between President Obama and his Cuban counterpart, Raul Castro, marked the most significant thaw in the two countries' relationship in decades, signaling that normalization of relations with Cuba, which President Obama announced last December, is proceeding.In the coming days, the U.S.