I don't think it's fair to dismiss South Korea's results as propaganda. They do indeed have serious contact tracing. I'm not sure how it is now, but when I was in Korea in March-June 2020, there was a website where anyone could see literally every positive COVID case (anonymized), and everywhere they'd been over the last 2 weeks. They obtain this information via credit card transactions and such because they know that that is more reliable than personal testimony's.

Although this would be a non-starter in the U.S due to privacy concerns, I don't deny that this was probably effective. At the same time I imagine cases were drastically underreported because testing positive would result in your whole office shutting down, potentially getting one fired. So there's no incentive to get tested unless you have no choice.