As with most every other threat, be prepared to shelter-in for awhile. A week should be sufficient with even the worst U.S. rioting. As others have stated, stay away from demonstrations on issues that are particularly volatile. I've been in and around a lot of protests/demonstrations/marches in Washington, D.C. over the past thirty years -- the tenor of each gathering varies depending on the cause.

Riots in the U.S. typically have been highly localized within cities. There have been fires associated with riots -- such as the civil rights uprisings of the 1960s in Washington, New York, Baltimore. But those don't become city-consuming conflagrations 'ala Dresden or otherwise necessitate mass evacuation.

I live two blocks from a street that was heavily damaged in 1960s-era rioting. The primary casualty of the riot were the value of the properties damaged and the businesses who had been leasing those spaces.

Neighbors who lived here in the 1960s recounted that era when America's cities (including DC where I live) were on edge after the Rodney King verdict in 1992 -- at which time there were several days of rioting in Los Angeles. They said they stayed indoors and that they could see and smell the tear gas. While the one street was heavily damaged (flames were visible from the U.S. Capitol steps a mile away), the homes on the adjacent blocks were undamaged. I recall that there was also concern about possibile riots if O.J. Simpson had been convicted in 1995. But he was not so those concerns were unrealized.

The Los Angeles riots of 1992 are worth studying.

http://timelines.latimes.com/los-angeles-riots/


Here's a listing of riots and other significant civil disturbances in U.S. history. Quite a long list:

https://en.wikipedia.org/wiki/List_of_incidents_of_civil_unrest_in_the_United_States





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