Since 2000 his primary professional home has been George Mason University in Virginia, United States where he is Professor of International Affairs in the Schar School of Policy and Government.
In 2022 he joined the United States Institute of Peace as a senior advisor for religion and inclusive societies.
Previously he was a visiting senior fellow at the Pew Research Center (2009–10), and an Adjunct Scholar at the RAND Corporation (2012–15; 2017-2018).
He is widely regarded as a leading expert on political Islam, Middle East affairs, and on Muslim communities in Europe and North America.
He has authored numerous book chapters and journal articles, contributed to publications such as the International Herald Tribune, The Guardian, The Atlantic, and Foreign Policy, and has consulted extensively for media, government and non-profit agencies.