It isn't "much slower" when you actually account for the time spent waiting for the server to come around, getting their attention to ask for the check, waiting for them to come back with it, waiting for them to do their lap and come back to collect the card, waiting for them to go run it, and finally waiting for the card to come back.
This weird system is one thing I don't enjoy about visiting North America. Where I live, you never deal with the servers for payment. When you're ready to leave, you just leave. Every restaurant has a payment desk near the door where they show you your bill, you tap your card and you're on your way.
No need for the waiter to walk away with my card if they have a mobile POS, as I mentioned above. Tapping my card and selecting a tipping option takes less time than even opening my camera app.
Ironically, many of the QR payment places I‘ve been to actually have these as well.
I get that jumping from a central POS to a device per waiter is an investment – but why switch to QR codes if all your staff is already equipped with a strictly superior solution?
In my experience, US restaurants either have something very new (i.e. combined POS/ordering handhelds), or very old (i.e. centralized/non-mobile, sometimes even magstripe only POS, no PIN or contactless capability).
The ones I‘ve seen that have switched to QR payments had mobile POSes before.
They have started appearing very quickly. There is definitely a long tail, but these days I would say I see one at least ever other time I go to a restaurant or bar.
