September 11th, 2001 changed the course of U.S. history substantially. The terrorist attack can be better understood by learning about the history of U.S. involvement in the Middle East. Many of the regimes the U.S. has supported, both in the Middle East and globally, have been led by brutal dictators that consistently violated human rights. In some cases we have assisted in toppling democratically elected governments to install these dictators. We have supported the Shah of Iran, Saddam Hussein, and the Mujahedeen who became the Taliban. Our actions were a form of terrorism. Here is a discussion about terrorism from above and below…and some additional information:
https://link.springer.com/chapter/10.1057/9781137552341_3
https://www.globalpolicy.org/component/content/article/169/36408.html
https://www.democracynow.org/2004/6/10/ghost_wars_how_reagan_armed_the