LAS VEGAS (Reuters) - President Barack Obama called on Congress on Tuesday to make good on plans to overhaul the U.S. immigration system and offer a path to citizenship for millions of illegal immigrants. Reflecting the growing clout of Hispanic voters, Obama traveled to Nevada little more than a week after his second inauguration to make the case for swift bipartisan action on immigration. "We need Congress to act on a comprehensive approach that finally deals with the 11 million undocumented immigrants," Obama said at a high school in Las Vegas. ...