Pretty sure China had no part in popularizing it and third party apps had support for it on iPhone a long time ago. I was seeing and using QR codes here in the US back in 2010 or so pretty commonly. They were limited to college campuses and SF bay area then but still were around plenty.
I remember being frustrated that my non-smartphone flip-phone didn't support them (and no way to add support for them either).
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.
I remember being frustrated that my non-smartphone flip-phone didn't support them (and no way to add support for them either).