What is left and right is very different by country and time. It’s not so simple that one can say that liberalism led to extremism in France. We are more liberal than them in some ways (affirmative action, etc.)
The Muslim immigrants are simply very different there. They let in the impoverished Muslim masses from their former colonies, while we (the US) let in the college-educated elite Muslims. We also have some extremism and terror attacks here too — Nidal Hassan killed 13, the Boston Bombers killed 3, the DC Snipers killed 10 (it’s unclear but they definitely seem to have been influenced by jihadi ideology), etc.