I think most people pay their balance off every month in the USA. Credit card doesn't mean borrowing. The big problem with credit cards in China is fraud: banks like ICBC will put the burden of proof on the card holder when a fraud transaction occurs, rather than the merchant as in the west. I really hate ICBC.
Anyways, debit cards work just like QR pay does, just like UnionPay already does. The problem QR codes are solving is the lack of a POS terminal and stream lining the swipe. Many countries have an even better technology in NFC contact (including China, many newer UnionPay POS's include NFC, though the card must have a chip to support it). Then you could just glue your debit card to the back of your phone...(or use NFC in your phone via something like Apple or Android Pay).
Anyways, debit cards work just like QR pay does, just like UnionPay already does. The problem QR codes are solving is the lack of a POS terminal and stream lining the swipe. Many countries have an even better technology in NFC contact (including China, many newer UnionPay POS's include NFC, though the card must have a chip to support it). Then you could just glue your debit card to the back of your phone...(or use NFC in your phone via something like Apple or Android Pay).