PSY is backtracking on that invisible horse of his. The hugely successful “Gangnam Style” rapper shocked many earlier today when anti-American statements he made at a protest concert in 2004 came to light. Among the incendiary lyrics: “Kill those f—king Yankees who have been torturing Iraqi captives/Kill those f—king Yankees who ordered them to torture/Kill their daughters, mothers, daughter-in-law and fathers/Kill them all slowly and painfully.” …