I suspect that in the case of the imams, they were a bit louder than they thought (aren't most us, often?), and that people around them who didn't speak Arabic and who were biased and uninformed heard what they expected to hear. And no, I doubt very much if everyone knows about the Muslim practices of prayer. Heck, there are a lot of people who believe that Catholics worship the statues of saints in their churches, and Catholics have been in mainstream awareness for a heck of a lot longer than Muslims have.

I wrote about the Ellison case a few days ago. A comment pointed out there, as knitmeapony does here, that Congresspeople aren't sworn in on a Bible as a matter of custom. However, apparently they can use one if they want to.