Homegrown terrorism, which is formally referred to as domestic terrorism is the kind of terrorism in which the terrorist targets the victims that carry the same citizenship as the terrorist. Such acts of terrorist are usually conducted without any strict motivation behind them.
Usually, homegrown terrorists happen to have some mental issues that they are facing. Other than that many homegrown terrorists are motivated from external terrorist organizations such as the ISIS and Al-Qaeda primarily because they support their ideology and want to spread the same acts of terrorism in their home country. Indeed, homegrown terrorism is quite widespread in the United States because of the vast majority and the high level of diversity.