Paypass apparently has started in Australia ($35 max) although I haven't actually found a terminal.
If you do find one, you may find it wont work on your US Mastercard (you can still swipe). When I was in NYC and tried to use Paypass, it failed. My bank (CBA) told me I can only use Paypass in Australia.
Also, if you have a Chip on your card, the credit card terminal may force the use of the chip (and refuse the swipe). The PIN is still optional.
The minimum is due to the banks charging around 2.5% on CC transactions. On small value items, there would be minimal profit if a card was used in preference to cash. The bigger stores can afford it for the loyalty (and due to their volume, probably have a lower CC commission).
I've bought a 50c cone at McDonalds on Visa (because I could!)
Evan :->