Sure. There is no conflict in being an American and a Christian; no point where one would have to make a choice, prioritize. No area where both claim supremacy.
Right. And my point is, there are not many (if any) Christian sects where one must make the choice. Sure, there are some (7th Day Adventists, I think) where you cannot take up arms and kill someone if asked by your government to do so, but you are allowed to serve in other ways and many have honorably done so.
However, there ARE branches of Islam that do bring followers directly in contradiction of the principles of their government, and often at a very basic level too. Not superficial things, either.