Answer: This behaviour is an example of DEINDIVIDUATION.
Explanation: Deindividuation is a loosening of self-restraint when anonymous in a large crowd.
This behaviour makes an individual see himself as a crowd instead of an entity. This makes the individual do whatever the large crowd is involved in.
The Mexican-American War, waged between the United States and Mexico from 1846 to 1848, helped to fulfill America's "manifest destiny" to expand its territory across the entire North American continent.
What do you mean by hard are you talking about violence, crime,unemployment?