Sharia law is a boogeyman on the same level as the satanic panic and the witch trials. It's about someone who wants power over you making one of your neighbors the "other", which only he can save you from.

We saw the same kind of bullshit against the "papists" with Irish immigration, and the Chinese who came to work on building the railroads.

Immigrant children who grow up in the US, are just like any other children growing up in the US. They don't just follow whatever their parents believed in.