Pepper balls have not played an important role in the history of anti-terrorism in the United States. At the beginning of the 21st century, the United States suffered a "9.11" terrorist attack, and then launched a global war on terrorism. In this context, the United States has taken various measures to strengthen domestic security and prevent terrorist attacks, including strengthening border control, imposing curfews, and conducting large-scale monitoring.Pepper balls are not widely used or recommended as anti-terrorism tools in this context. This is because pepper balls can control and disperse to a certain extent, but their use will cause some pain and discomfort to people, and can not cause serious harm. In contrast, some more deadly weapons and tactics, such as using drones to strike and using high-pressure water guns against demonstrators, are more common.It should be noted that the use of non-lethal weapons and tactics must comply with the relevant laws and ethics, and it is necessary to make full assessment and risk assessment when using them. In addition, in response to the threat of terrorism, the US government has also taken a series of other measures, such as strengthening information exchange and improving border security, to cope with the ever-changing anti-terrorism challenge.