Ehh, I work in one of the regions you name in a practice with many APPs, and I would say the statement that a neurology APP is filling a general neurology position is equivalent to saying a PA that manages uncomplicated hypertension all day is filling a fellowship-trained cardiology position.
APPs are excellent at dealing with uncomplicated migraine, uncomplicated neuropathy, uncomplicated memory loss ("worried well" or pseudodementia). You could argue that a neurologist could see all of those and bill for them, but could also argue that a PCP could (and should) be able to manage basic headache, diabetic neuropathy, etc.
I enjoy working with APPs and they do see a lot of patients, and at least where I work do a good job of it. But there's zero competition between us. They couldn't do my job, and any place that's using an APP instead of paying a neurologist is probably having a ton of trouble attracting a neurologist in the first place. I'm sure you've seen the job postings these days.