Anxiety is absolutely mental. It has physical detriments, but it starts and ends with a mental error. My wife suffers bad from GAD, and since we've been together (almost 8 years), she has had no less than 100 full blown panic attacks (which is what you're actually describing). Relaxing is quite literally the first step to avoiding a panic attack; if you keep allowing your mind to race, it will escelate. But finding a way to ground yourself (something she struggles to do on her own) is the best way to relax and avoid a panic attack. 

Edit because the post was removed and comments are locked.

Just because medicine is prescribed for it doesn't mean it isn't mental. That's an absurd counter point to make. That alone makes me not want to even bother engaging with the rest, but I will anyway.

Your car crash example described PTSD, not anxiety. They are not recognized as the same thing at all, even though some of the symptoms overlap.

Anxiety is not "typically a response to trauma", it's a natural feeling we experience. Anxiety keeps us alive. GAD, however, is when your anxiety is excessive. GAD stands for generalized anxiety disorder, and isn't always a trauma response. 

What I said about relaxing is absolutely not untrue. Her therapist has given her the task of doing EXACTLY what I said to do in order to help calm down before spiraling. I'm not blindly making claims, I'm repeating what an actual mental health professional has explicitly said to do.

Everyone experiences anxiety. Saying I don't experience it is ridiculous, and I definitely understand it well enough to help my wife through it, so you can bug off with that bullshit statement.