I have not entered your poll because, as with many others here, I do not readily fall into the arbitrary categories. However, that is not to say that yours is not an interesting and thought provoking question, or that I do not have a point of view on the matter.
Any -ism is essentially ideological, and the definition published in the Wikipedia is merely the view of the contributor/s concerned. The term American Exceptionalism is used variously, and there is no universal definition governing its use.
Is the USA as a society, and are Americans as a people, exceptional? I would say so, but only to the extent that every society is atypical in many ways. Do I believe in American Exceptionalism - of course not! The term and concept is redolent of inherent and intrinsic superiority, and is as ridiculous as believing in intrinsic conservative or socialist superiority. We are all different, with varying strengths and weaknesses.
There is no best country on earth, and none of us is inherently superior, irrespective of our geographic location, or socio-political beliefs. That is a nonsensical and puerile concept.
It is my view that Americans are accomplished enough, intelligent enough, and generous enough, not to have to bolster their self-confidence with such adolescent self-promotion. You simply have no need of it.