In some places, there is definitely a religious culture. A few weeks ago, I was in a state government building, where Jesus and the Lord were mentioned several times in a meeting. I've been in a bagel bakery and have been wished a "happy holiday" and realized that the holiday was Rosh Hashana.

All depends on the neighborhood. But, yes, the presumption that you're Christian and, of course, would have Jesus, is common in some areas.

What strikes me is that it'd rather un-Christian to spite someone by charging them more for a sandwich. If she thinks you need saving, then ripping you off on your food purchase is the wrong way to go. If bringing you to Jesus is important to her, then she should just come out and try to convert you. If keeping quiet is more important to her (perhaps because her boss told her not to preach religion on the job), then charging you extra seems to be a lousy was of accomplishing her goal of spreading the Word.

Not that I doubt this. History is filled with people using all sorts of petty and not-so-petty (genocide) examples of coercion to non-believers.