WASHINGTON — After a year of high-profile police shootings of black Americans, many captured on video, racial attitudes among Americans – particularly whites – have undergone a significant shift. A majority of whites now say the country needs to do more to make equal rights a reality, and a significantly larger number of white Americans say blacks are treated less fairly than others by law enforcement officials, according to several newly released polls. The share who say racism is a “big problem” in the U.S.