I don't think "American Exceptionalism" is even something you agree with or don't. It's vaguely defined, and even when you try to narrow it down to a somewhat specific definition there are some ways I would agree with it and others I wouldn't. Like, our rise in stature, wealth, and power in the first half of the century was absolutely unprecedented and "exceptional", but that doesn't mean that American people or the American nation is inherently better than others.