The first python meetup I went to in SF (back in 2013) had 300 spots and a waitlist that I doubt got cleared. The NYC meetups I went to managed maybe 80 RSVPs and a couple dozen who actually showed up.
Once you get to anything more specialized than a programming language meetup, it's basically non-existent anywhere else in the country, but the bay area will still manage an active user group.
I really wish this weren't the case, and I really resisted moving here. I had every expectation I'd hate it and the city has more than lived down to expectations (easily higher rent and worse crime than NYC - or least the tech enclaves of NYC where I spent my time - by healthy margins). It is absurd and frankly unjustifiable how densely tech is concentrated here. But that it is so isn't really debatable.