I lived in SF in the 2010s... QR code adoption was abysmal. I'm not saying China wis why we adopted QR codes, but because the QR code function was part of the main UX of their main platform (Wechat app), there was massive adoption of QR codes before the US started doing so in the late 2010s because our major platforms (Android, iOS) started integrating it into the core UX.