Just days after the United States celebrated its 240th birthday, people in interviews across the country said that the nation increasingly felt mired in bloodshed and blame, and that despite pleas for compassion and unity, it was fracturing along racial and ideological lines into angry camps of liberals against conservatives, Black Lives Matter against Blue Lives Matter, protesters against the police. Whose side were you on? Which victims did you mourn?

In a televised interview, the executive director of the National Association of Police Organizations blamed President Obama for waging a “war on cops.” On social media, others confronted the discrepancies in the everyday lives of black and white Americans, hoping understanding would lead to conversations and action.

Along the Las Vegas Strip, a sunbaked cross-section of races, backgrounds and political views, tourists and workers said the relentless parade of violence during the week had left them mostly in shock and disbelief. They worried that more would follow…

Ms. Berry, the teacher in Iowa, said she worked hard to raise her two boys, Dallas, 15, and Amari, 11, to make a good impression. Square your shoulders, she has always told them, look people in the eyes when they talk to you, and stand up for what is right. But that advice comes with a painful exception: Do none of these things if stopped by the police.