Interesting question and, not being a professional, I can't say I really know. What I can say is that J's anxiety seems to be much much higher than my son's, and somewhere in-between then is probably where that line between AS anxiety and co-morbid anxiety is.
My son doesn't have any "generalized" anxiety; we can always find a specific reason for it that goes back either to a negative experience or a sensory issue. If my son appears to have more anxiety than the average kid, it is only because life really is more difficult and anxiety producing for him. Because of his difficulties in other areas there are more opportunities for events that cause it. Social issues will cause anxiety; homework with too much use of his hands will cause anxiety; a page with too many problems on it can cause anxiety because he doesn't have the executive function to manage it; he gets anxious around dogs because of a terrifying experience with one when he was very young; and so on. It usually relates to something that is more difficult for him because of his AS, but by itself it isn't normally caused by the AS.
Does that make sense? Things you can find a rational trigger for, v. those you can't?
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).