She is the founder and executive director of the nonprofit organization If Americans Knew (IAK), president of the Council for the National Interest (CNI), and author of Against Our Better Judgment: The Hidden History of How the U.S. Was Used to Create Israel.

After several months, she decided that "this was perhaps the most covered-up story I had ever seen" and quit her job in order to visit the West Bank and Gaza, where she wrote about her encounters with Palestinian suffering and with the "incredible arrogance, cruelty, selfishness" of Israelis.

[4][non-primary source needed] Weir's official biography says her activism draws on her history of involvement in the American Civil Rights Movement, her work in the Peace Corps, and her childhood in a military family.

Weir has partnered with white supremacists and Holocaust deniers including Christian Identity leader and conspiracy theorist Clayton Douglas and American Free Press, both designated as hate advocates by the Southern Poverty Law Center.

[7][10] On Douglas' radio show, Weir "dismissed allegations that he was a racist, did not challenge his repeated assertions of Jewish control of the world, and did not protest when he played a speech by former Ku Klux Klan grand wizard David Duke.

[14] In June 2015, Jewish Voice for Peace (JVP) stated that they chose not to work with Weir, on the grounds that "she has consistently chosen to stay silent when given the opportunity to challenge bigotry, which we find repugnant.

[18] More than 2,000 activists[citation needed] signed an open letter supporting Weir, including former United Nations Special Rapporteur on the Palestinian Territories Professor Emeritus Richard Falk; founding member of Birzeit University's board of Trustees Samia Khoury; Palestine Rapprochement Center Director/ISM co-founder George Rishimawi; activists Hedy Epstein, Ann Wright, Arun Gandhi, Ray McGovern, Cindy Sheehan, Greta Berlin, Paul Larudee, Philip Giraldi and James Petras; American-Arab Anti-Discrimination Committee founder and former Senator James Abourezk; and many members of JVP itself.

[13] CNI describes itself as seeking to "encourage and promote a U.S. foreign policy in the Middle East that is consistent with American values, protects our national interests, and contributes to a just solution of the Arab-Israeli conflict.

It is CNI's goal to restore a political environment in America in which voters and their elected officials are free from the undue influence and pressure of foreign countries and their partisans.