Do you think Christians look down on non-Christians?

That’s a foolish argument and you know it. You’re arguing that it’s incorrect to talk about belief or disbelief because these folks don’t think there’s any such thing to believe in. Do you honestly not see the problem with that statement?

Yes a lot of Christians think they are on the right path. Therefore you are not.
A lot of Jews think they are the chosen people.
A lot of Muslims think they are the only ones with real answers .Etc.Etc,.Etc.
It is a characteristic of religion. If you are a believer that you are on the right road, then every one who is not in your religion, must be wrong. Why don’t they just understand the absolute truth that you have managed to obtain? What is wrong with these people who are just so wrong?

It isn’t a foolish argument at all. It’s really just a statement of fact.

As an atheist, I am dubious about any assertion that means that “I don’t believe in that” is an impossible statement to correctly make.

Put simply, saying that something doesn’t exist is a statement of disbelief.

But how much of that comes from actual differences in politcal thought as opposed to how much comes from having religion deeply involved in the politcial thought in America?

Yes “Christians” look down at others, people who practice christianity don’t. But it’s a two way street. Many Atheists and Agnostics look down at anyone who believes anything.

There always have been “Christians” and “people who practise”, certainly if Chaucer’s any kind of a recorder. Among all the frauds, fakers and humbugs in the Canterbury Tales there was the honest Vicar, who “Christ his lore and his apostles twelve/He taught; but first he followed it himself”.