Americans are bracing for a summer of racial disturbances around the country, such as those that have wracked Baltimore, with African Americans and whites deeply divided about why the urban violence has occurred, a new Wall Street Journal/NBC News poll has found. A resounding 96% of adults surveyed said it was likely there would be additional racial disturbances this summer, a signal that Americans believe Baltimore’s recent problems aren’t a local phenomenon but instead are symptomatic of broader national problems. When asked to explain recent events in Baltimore and other cities that have seen confrontations between police and members of...