Reuters: More than 32 million Americans watched U.S. President Barack Obama address the nation on the Gulf of Mexico oil spill on Tuesday — a 33 percent drop in audience size for his first State of the Union speech in January. Figures from TV tracker Nielsen on Wednesday showed that 11 network and cable channels carried Obama’s national address live from the Oval office, drawing an overall audience of 32.05 million people. In comparison, just over 48 million Americans watched Obama’s …