QR is a poor substitute for contactless. America has screwed up their chips, however, making even contactless pay too slow, I can't imagine QR codes would improve anything unless the money was onloaded somehow (like how it works at Starbucks).

American EMV has some dumb decisions baked in, but as far as speed goes it's not the chips, it's the existing in-store backend processors. A lot of them are over slow and unreliable connections (GPRS is super-common, as are phone lines shared by many points of sale). As processors are forced to upgrade, Americans are seeing faster chip transactions.

Companies that prioritize this--Walgreens comes to mind as an obvious example--have chip auth under ten seconds. It isn't optimal, but it's improving.

Even stores with faster connections like grocery stores in bigger cities it is "wait a few seconds" (less than ten, they have it down to 3-5 seconds at this point) and then collect the receipt after it slowly prints out.

Whereas in Australia, it is just "tap and go." Starbucks works similarly with their QR code buying (but the money is onloaded to a digital gift card; but then I never use it anymore since mobile ordering is so damned convenient).

Can't speak to Australia. My barometer is Europe; in urban England it was still five seconds and in rural France it was worse than at home.

(I agree it's less than ten, I just couldn't remember any off the top of my head that I felt confident asserting.)