Actually it's the 1st and 14th Amendments. There are a lot of Salafists in the US. They despise terrorism, and their way is build up culture, have lots of children, and lead by example.
There is no active Government interference in worship like in France and people's reaction to Niqabis is meh.
You will never see US Police assaulting women in the streets or beaches over their attire and denying girls public services over their dress like France.
In short, French hypocrisy is driving the problem. The French voted for this as well, so you French made your bed. Now lie in it. Or you know, stop being hypocritical assholes easily manipulated to vote for neoliberal politicians who sell you out after swearing in.
Are US Salafis well-educated or poorly educated on average?