> That could be mitigated if you had so many coffee shops that none of them were busy enough for those externalites to matter (e.g. at most a handful of cars out front), but a coffee shop that slow may not make enough money to actually survive.

As many of them would survive as could be sustained. You don't get a situation where there are too many and then they all go out of business, you just increase the number until the constraint hits how to cover the now-lower costs instead of it being the locations where one can be built to begin with.

Your premise is that the median one couldn't survive unless it was inundated, but that's contrary to all the currently operating ones in locations where that isn't happening.

> So you may have a natural and legitimate resistance to more, because of the externalites.

What really happens is that people look at the traffic at one when there is a severe constraint on where they can be built and expect that to happen everywhere without that constraint, when the constraint is the reason for the traffic being concentrated in that one place to begin with.

> Grocery stores and coffee shops are like 10-15 minute drive away from most suburban homes, and there's never a jam.

The problem is the example was "45 minutes" which is actually pretty excessive, whereas the overall issue is "have to sit in traffic or circle to find parking to get there".

And then isn't your contention here contrary to your previous premise? If there is no traffic with that number of shops, what result when there are more, smaller shops so that each one has less traffic than that?