Improving growth, falling unemployment and a sense that the U.S. is returning to "normal" could fuel a 20 percent stock market gain and make 2011 the "Year of the USA," according to Goldman Sachs  economist Jim O'Neill.

O'Neill, the widely-followed chairman of Goldman Sachs Asset Management, in a note this week made the case for the U.S. to be a bright spot in the world economy, with growth rates of 3.4 percent in 2011 and 3.8 percent in 2012.