Some autistic people experience high levels of anxiety in social situations.

If they're diagnosed as autistic they get suitable help.

If they're not diagnosed as autistic they get treatment for Social Anxiety or Social Anxiety Disorder, and that treatment doesn't work because they don't have SA or SAD.

To expand on this further, anxiety itself isn't a bad thing, as long as it has a good reason and is in a reasonable amount. People with an anxiety disorder feel far too much anxiety to the point is harms them. An autistic person who experiences anxiety about a social situation isn't experiencing extra anxiety because they experience too much anxiety compared to the average person, but because their relationship with social situations, due to their autism, has given them valid reasons for having more anxiety than the average person. Their anxiety is valid, thus fixing it by trying to treat it as stemming from a source giving them too much anxiety is fixing the symptom instead of the problem.

It's the difference between someone with arachnophobia fearing a toy spider like it was a real danger and someone who is susceptible to black widow poisoning fearing a black widow because it is a greater danger to them.

I'm in a similar borderland, I'm diagnosed ADD, and my daughter ADD with autistic traits.

Doesn't make me the best person to answer, but I also felt the responses to be weird. But I'll relate some of my experiences, if they might be of some use.

I'm not an expert in anxiety by any means, however, one thing that stands out to me is that when my daughter is feeling anxious about something, let's say it would be about the state of geopolitics - or whatever - I could calm her by telling her that it is in fact a rather dire situation. That is, if this is representative, that the uncertainty in/about/through your own interpretation is often more disconcerting than even the worst case scenario. Similarly, I've had friends tell me: Yep, you are being an idiot! Which is accompanied by a figurative, if not literal sigh of relief from me.

While this probably isn't completely alien in anxiety in general, it seems much more pronounced for people close to, or on the spectrum.

For some I also believe a weaker/different perception of time plays a significant role in the difference. Maybe this is more my ADD side, but time can become invisible, everything is a moment which encompasses all of time. Ancient, yet newborn and without temporal roots.

Hence some anxiety might not be as much about the future, but of this current eternal now and all that has been. I rarely get embarrassed even if I done something mind boggling stupid, but I can sometimes get anxious about small things that happened decades ago, of which the outcomes have certainly completely played out. It's as if cause and effect isn't always causally ordered in my subconscious brain, hence the memory evoked doesn't evoke the appropriate emotional state.

Got a real headache, so I'll stop typing now. Quite likely mostly gibberish anyway, tends to become such when I'm in this state, against my best intentions. But hey, practice makes perfect, eh :)

Off-topic, but I subscribe to the notion that ADD and ASD share a broader spectrum if not a common neurological pathology. DSM-V changed the rules overnight and now it’s very common for ASD and ADD comorbidity to be positively diagnosed. My personal, lay-person (but diagnosed) opinion is both spectrum definitions are “wrong” and I hope we’ll have more objective diagnostic criteria in the near future.

An issue with ASD is the prevalence of higher intelligence levels that mask occurrence of ADD - until those people advance their education or careers until a point where it becomes a problem - and then it becomes a real problem.

Do you have an opinion or position on the subject of ASD/ADD comorbidity?

Well the only ressource I have is my experience. I endured severe anxiety from childhood, instead of reading "normal" books at my early age I was into astrophysics and it lead me also to ask to myself why I was here down earth, the purpose of life blabla. It was in France. My mother thought I was just way too much anxious about nothing and told me to breath properly while I was doing panic attacks every single nights... But in the end I had only myself to rely on and I ended up studying people's behaviours to fit a bit into the society. Now if you interact with me of course I won't be amazingly extrovert although my Asperger's traits aren't that obvious now if you spend a short amount of time with me. But to be honest, because of a huge misdiagnosis in France I've spent 12 years under the wrong treatments while I was simply an aspie. Now I'm still taking some medications, because you know, you can't get rid of all of those medications cold turkey, and my psychiatric treatments and journey turned into a punitive one. But there's worse.

Edit: During my Master's degree I spent one year studying remotely because of agoraphobia, stuck in my student room. Social anxiety is something I'm kind of used to deal with now... But it didn't blocked me to travel and work abroad. :)

For one thing, anxiety isn't always a root cause. If you are autistic your anxiety may have roots in sensory issues, different from anxiety experienced by someone with schizophrenia.

Well for one stressors are different - in addition to sensory issues that aren't common things like not finding awkward silences awkward. Stimming probably wouldn't prove helpful to neurotypicals for an example backwards.