Back when al-Qaeda was the focus of attention, you heard plenty about people, including Americans and other Westerners, being radicalized by them and/or via a system of radical madrassas (mostly in Pakistan) and radical networks (throughout the world) associated with them and their ideology.
It's true that the mechanisms were different, because social media wasn't a big thing at the time: John Walker Lindh was radicalized before the services that really made "social media" a global force existed.
It's true that the mechanisms were different, because social media wasn't a big thing at the time: John Walker Lindh was radicalized before the services that really made "social media" a global force existed.