The defendants were convicted of the 1993 World Trade Center bombing and planning a series of attacks against New York City landmarks.

He defended false claims that the Affordable Care Act would lead to "death panels", and promoted a conspiracy theory that Bill Ayers, co-founder of the militant radical left-wing organization Weather Underground, had authored Obama's autobiography Dreams from My Father.

[5] McCarthy led the satellite office of the Southern District, in White Plains, New York, for five years, where he investigated the 1998 bombings of United States embassies in Kenya and Tanzania.

[9] After the September 11th attacks in 2001, McCarthy's became a key member of a command team of prosecutors tasked with drafting search warrants and "connecting dots" in the ensuing investigations.

[8] McCarthy is currently a senior fellow at the Foundation for Defense of Democracies, serving as the director of the FDD's Center for Law and Counterterrorism.

From the country’s perspective, it’s not a good thing.” A prosecutor's job, he added, “is not the national security of the United States.”[8] He criticized the Obama administration for trying suspected terrorists in civilian courts.

[8] In February 2007, McCarthy authored an endorsement for the fledgling candidacy of Rudy Giuliani during the 2008 presidential election campaign in the National Review.

[citation needed] During the 2008 presidential election campaign, McCarthy wrote a number of posts on the National Review's Corner blog stating that he thought that Democratic presidential candidate Barack Obama was not serious about protecting United States national security against threats from Islamic extremism and elsewhere, and that Obama had a number of troubling ties and associations with leftist radicals.

McCarthy promoted the conspiracy theory that Bill Ayers, co-founder of the militant radical left-wing organization Weather Underground, had authored Obama's autobiography Dreams from My Father.

"[20][24] In May 2009, McCarthy provided details of a letter declining an invitation from Attorney General Eric Holder for a round-table meeting with President Barack Obama concerning the status of people detained in the War on Terror.

[33][34] McCarthy has stated on Fox News that he supports gun violence restraining orders as a tool for American law enforcement to remove firearms from those found to be a danger to themselves and/or others.

After the January 6, 2021 attack on the United States Capitol, McCarthy wrote that he now considered Trump's presidency "indelibly stained" and wrote, "I do think the president has committed an impeachable offense, making a reckless speech that incited a throng on the mall, which foreseeably included an insurrectionist mob."